JPH08105846A - X-ray analyzer - Google Patents

Abstract

PURPOSE: To provide an X-ray analyzer for realizing DAFS measurement on a laboratory scale. CONSTITUTION: An X-ray emitting position is varied while Rowland conditions are met so that an X-ray emitting point by an X-ray source 2, a radius of curvature of a concave diffraction grating of a crystal X-ray monochromator 3 and an X-ray condensed focus position are always on a Rowland circle. Changing the X-ray emitting point is performed by changing an incident position of an electron beam 16 into a target 11 by deflection, while the angle of the crystal X-ray monochromator 3 and the radius of curvature of the concave diffraction grating are varied synchronously with the change, and the X-ray emitting point, the radius of curvature of the concave diffraction grating and the condensed focus are controlled so that they are always on the Rowland circle. With this constitution, while a goniometer and the X-ray source which are difficult to move are fixed at a position, energy of the X-rays incident to a sample is swept, wherein intensity of the X-rays diffracted by the sample is measured to perform DAFS measurement on a laboratory scale.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray analyzer for material evaluation and structural analysis of semiconductor materials and the like, and more specifically to a diffraction E combining an X-ray diffraction method and an EXAFS method.
The present invention relates to an X-ray analysis apparatus capable of performing X-ray analysis by the XAFS (DAFS) method on a laboratory scale without using high-intensity X-rays of a synchrotron radiation experimental facility.

[0002]

2. Description of the Related Art A method of measuring by X-ray diffraction is known as a method of structural analysis of a material at an atomic level. This is a phenomenon in which when a sample is irradiated with X-rays, strong reflection (diffraction wave) occurs only in the direction determined by the wavelength of the X-rays and the crystal plane spacing due to interference of waves reflected on the crystal plane of the sample. Is based on. By measuring the intensities of the diffracted waves from the crystal planes in many different orientations, it is possible to obtain knowledge about the crystal structure of the sample. However, since this method cannot be used for diffraction of a substance having no crystal structure or a non-solid substance, in such a case, amorphous analysis is also possible.
XAFS (Extened X-ray Absorption Fine Structure)
) Method is used. The EXAFS method is a method of analyzing a vibration structure seen in the energy spectrum of the absorptance appearing at X-ray energy higher than the absorption edge where the X-ray absorption changes greatly. However, EXAFS requires X-ray counting of about 1 million counts for one energy when X-rays are swept in the energy region above the absorption edge, so it is high to complete the measurement in a practical time. Intense X-rays are required. In order to obtain this high-intensity X-ray, we have to use a synchrotron radiation experimental facility,
It cannot be easily measured at any time.

Therefore, an apparatus for measuring the EXAFS has been developed on a laboratory scale. This device uses a curved dispersive crystal to disperse and focus X-rays and irradiate the sample.
The intensity of the transmitted X-rays is detected by an X-ray detector. FIG. 7 shows an example of a conventional configuration of this laboratory EXAFS.
As shown in FIG. 7, in the laboratory EXAFS analyzer,
The X-ray source is large in size to obtain the highest possible X-ray intensity, and it is difficult to move, so the position is fixed, and in order to use the X-ray efficiently, a spectroscopic element 42 using a curved crystal is placed on the Roland circle 41. The X-ray emission point S, the spectroscopic element 42, and the converging focal point F are always arranged in the dispersive crystal 42.
It is set so as to be on a Roland circle 41 having a radius of curvature of as a diameter, and energy is swept by continuously changing the incident angle and the reflection angle of the X-ray with respect to the spectroscopic element 42 while satisfying the Bragg condition. Since the X-ray source is fixed, the spectroscopic element 42 and the focusing point F are moved together. For example, as indicated by the broken line in the figure, when the spectroscopic element 42 is moved in the x-axis direction, the focus F is also moved to F ′. This movement is caused by the distance between the X-ray emission point S and the center A of the spectroscopic element 42, the focus F and the center A of the spectroscopic element 42.
If the distance between and is equal, then ∠SAO = ∠OAF,
∠SA'O '= ∠O'A'F, and the incident angle and the reflection angle can be swept by continuously changing this. By arranging the sample to be analyzed at the converging focal point F, or by providing an exit slit for the condensed X-ray, the X-ray energy can be swept to the sample. In addition, DAFS (Diffraction Anomalous Fine Structu) combining the above X-ray diffraction and EXAFS
re) method is being developed. This is the incident X near the absorption edge.
This is a method of measuring the intensity of X-rays diffracted by the sample while changing the energy of the rays. Although ordinary X-ray diffraction and EXAFS can only obtain information about the average structure of the whole substance, DAFS has a feature that information on different atomic positions in a unit cell in a crystal can be separated and analyzed. However, this DAFS also needs to use the high-intensity X-rays of the synchrotron radiation experimental facility, like the EXAFS. Therefore, the inventor of the present application considered that DAFS can be realized on a laboratory scale without using a synchrotron radiation experimental facility by combining the above-mentioned laboratory EXAFS and X-ray diffraction.

[0004]

However, in order to realize DAFS on a laboratory scale by combining the experimental system EXAFS and X-ray diffraction, it is necessary to clear the following problems. It is difficult to move in the laboratory EXAFS because the X-ray source is upsized in order to obtain the X-ray with the highest possible intensity. Therefore, the X-ray source is fixed and the sample and the detector can be moved. However, in X-ray diffraction, the orientation of the crystal axis of the sample is aligned with the direction of the incident X-ray in an appropriate direction and rotated in a desired direction, and the X-ray diffraction intensity in various directions is detected. A goniometer is required to rotate the instrument around the sample. This goniometer requires high-precision rotation accuracy and needs a drive system for automatic measurement, resulting in an increase in size and weight. Therefore, it is very difficult to incorporate such a goniometer into the EXAFS of the laboratory system. Also, the EXAF of the laboratory system
In S, the light is focused to obtain a strong X-ray intensity, so that the X-rays are incident on the sample with an angular distribution of 2 to 5 degrees. However, in X-ray diffraction, diffraction occurs only under a diffraction condition in which the angle between the incident X-ray and the crystal plane is in the range of several seconds to tens of minutes.
The use range of the wire is narrow and the measurement time cannot be shortened. The inventors of the present application have attempted to solve the above problems in order to realize DAFS on a laboratory scale, and have developed an X-ray analyzer that realizes DAFS on a laboratory scale. Therefore, it is an object of the present invention to provide an X-ray analyzer that realizes DAFS measurement on a laboratory scale.

[0005]

In order to achieve the above object, the means adopted by the present invention is the emission point of the X-ray emitted from the X-ray source, and the above-mentioned X-ray is dispersed and condensed by a concave diffraction grating. The X-ray source and the spectroscopic element are arranged such that the spectroscopic element and the X-ray focusing point by the spectroscopic element are located on a Rowland circle whose diameter is the radius of curvature of the concave diffraction grating. And an X-ray analyzer having an X-ray detector mounted so that the sample is located at the focusing point, and the goniometer is formed on a cylindrical surface along the circumference centered on the spectroscopic element. An X-ray source for changing the emission point position of the X-ray by changing the incident position of the electron beam incident on the target, and an X-ray for the spectroscopic element in synchronization with the change of the emission point position of the X-ray. Incident angle of line An X-ray analysis comprising a spectroscopic element driving means for changing the radius of curvature of the concave diffraction grating, and a goniometer in which a rotation axis for holding the sample is fixedly arranged on the Rowland circle. It is configured as a device. In the above structure, the X-ray detector may be a position-sensitive X-ray detector. Further, the electron beam incident surface of the target can be adopted as a cylindrical surface.

[0006]

According to the present invention, the Roland condition is satisfied in which the X-ray emission point, the radius of curvature of the concave diffraction grating of the spectroscopic element, and the focal point of the spectroscopic element are always located on the Rowland circle. While changing the X-ray emission point position.
The change of the emission position of the X-ray changes the emission position of the X-ray emitted from the electron beam incident position of the target by changing the incident position of the electron beam on the target by the deflection operation. The angle of the spectroscopic element and the radius of curvature of the concave diffraction grating are changed by the spectroscopic element driving means in synchronism with the change of the X-ray emission point position, and the X-ray emission point and the radius of curvature of the concave diffraction grating of the spectroscopic element are constantly changed. The focus is controlled so that it is on the Rowland circle. With this configuration, it is possible to fix the position of the goniometer that holds the sample placed at the focusing position of the spectroscopic element. Further, since the change of the emission point of the X-ray is an electric position movement, the X-ray source itself can be fixed in position. Therefore, an experiment was conducted by measuring the intensity of X-rays diffracted by the sample while sweeping the energy of the X-rays incident on the sample while the position of the large and heavy goniometer and the X-ray source, which are difficult to move, was fixed. DAFS measurements can be performed on a room scale. Claim 1 corresponds to this.

In the above structure, since X-rays are incident on the sample at a light collection angle collected by the spectroscopic element, a position-sensitive X-ray detector is used as the X-ray detector for detecting the diffracted light from the sample. Therefore, the angle information is position sensitive X
It is converted into position information on the line detector, and angular scanning by the goniometer can be performed substantially at once. Therefore,
Since the measurement time can be shortened, practical laboratory scale DAFS measurement can be performed without using high intensity X-rays.
Claim 2 corresponds to this. In addition, the target surface, which is the X-ray emission point, must generally be formed as a quartic curve, but a cylindrical surface centered at the center of the dispersive crystal is sufficient to obtain the energy change necessary for DAFS. Since they can be approximated, there is an advantage that the target can be easily manufactured. In particular, when the dispersive crystal is used for symmetrical reflection, that is, when the incident angle and the outgoing angle of the X-ray to the dispersive crystal are equal, the X-ray emission point and the sample should be arranged on the circumference centered on the center of the dispersive crystal. The Roland condition can be strictly satisfied.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. still,
The following example is an example embodying the present invention and does not limit the technical scope of the present invention. Figure 1
1 is a schematic diagram showing a configuration of an X-ray analysis apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view showing a configuration of a crystal bending mechanism according to an embodiment, and FIG. 3 is a crystal X-ray monochromator according to an embodiment. Fig. 4 is a schematic diagram for explaining the operation of the Johansson type monochromator used, Fig. 4 is a graph showing an example of measurement data stored in the multi-channel analyzer according to the embodiment, and Fig. 5 is a Roland circle accompanying movement of the X-ray emission point position. Explanatory drawing explaining the state of change, FIG. 6 is a graph which shows the example of a DAFS spectrum. In FIG. 1, an X-ray analysis apparatus 1 according to an embodiment includes an X-ray source 2 that irradiates a target with an electron beam to generate X-rays, and an X-ray having a specific energy from the X-rays emitted from the X-ray source 2. Crystal X-ray monochromator (spectroscopic element) 3 that diffracts and focuses only the rays and irradiates the sample 6 set on the goniometer 5, and a position-sensitive proportional counter that detects the X-rays diffracted by the sample 6. (X-ray detector) 4
And a data analysis device equipped with an analysis circuit 7 for analyzing and processing the detection output of the position-sensitive proportional counter 4, a multi-channel analyzer 8, an arithmetic unit 9 and the like, and synchronized with the scanning of an electron beam by the X-ray source 2. Then, a controller 10 for controlling the crystal X-ray monochromator 3 is provided. The X-ray source 2 generates X-rays by irradiating the target 11 placed at a predetermined position in the vacuum container 13 that is evacuated by the vacuum pump 12 with the electron beam 16. The electron beam is accelerated to 30 to 60 kV and is deflected by the deflection electrode 14 so that the target 11
Is irradiated. The generated X-rays are extracted into the atmosphere through a beryllium window 15 provided in the vacuum container 13 and irradiated on the crystal curved surface of the crystal X-ray monochromator 3. The electron beam irradiation surface of the target 11 is formed on a cylinder along a circumference centered on the dispersive crystal, and the position of the X-ray emission point is changed by the change of the electron beam irradiation position by the deflection electrode 14. be able to.

The crystal X-ray monochromator 3 is constructed by mounting a crystal bending mechanism 17 as shown in FIG. 2 on a rotary stage 18. This crystal X-ray monochromator 3
Is basically configured as a Johansson type monochromator. In the Johansson type monochromator, as shown in FIG. 3, the X-ray emitted from the emission point S of the X-ray toward the center of the dispersive crystal 19 and the X-ray having the same wavelength emitted in a different direction from the dispersive crystal 19 are incident on the dispersive crystal 19. The light is diffracted and focused on the focus F. The condition for diffracting light by the dispersive crystal 19 and condensing the light is such that the X-ray emission point S, the converging focus F, and all the converging focal points F are set so that ∠SAF and ∠SA′F are the same according to the theorem of constant circumferential angle. Set so that the diffraction point is on the Roland circle. Further, in order to make the incident angle of the X-rays on the crystal plane of the dispersive crystal 19 constant, the normal line of the crystal plane is directed on the circumference toward the point O opposite to the center of the dispersive crystal 19. To This is also proved by the theorem that the circumferential angle is constant, that ∠SAO and ∠SA'O are the same, and that line segment AO and line segment A'O are normals to the crystal plane. The dispersive crystal 19 has a crystal bending mechanism 17
The bending angle is adjusted so that the radius of curvature is twice the radius R of the Rowland circle by the mechanical pressurization by the drive motor 20 provided in the. Further, the incident angle of the X-ray is adjusted by rotating the rotary stage 18 equipped with the crystal bending mechanism 17. The change in the curvature of the dispersive crystal 19 by the crystal bending mechanism 17 and the change in the incident angle of the X-rays on the dispersive crystal 19 are input to a drive control device (not shown) mounted on the crystal X-ray morphometer 3. It operates according to a control signal from the controller 10.

In the above structure, the X-ray projected from the irradiation point of the electron beam 16 irradiated on the target 11 of the X-ray source 2 as the emission point of the X-ray has only a specific energy in the crystal X-ray monochromator 3. The sample 6 is diffracted, condensed, and set on the goniometer 5 at the focal point of the condensed light. The X-rays diffracted by the sample 6 are detected by the position-sensitive proportional counter 4, converted into position information by the analysis circuit 7, and then displayed on the multi-channel analyzer 8.
The detection result is stored as shown in the example. The controller 10 includes the crystal X-ray monochromator 3 and the X-ray source 2 described above.
The deflection angle controller 21 is controlled synchronously to change the deflection angle to change the X-ray emission point position from S to S as shown in FIG.
When moved to S ′, the rotation angle of the crystal X-ray monochromator 3 and the radius of curvature of the dispersive crystal 19 are changed, and the sample 6
The X-ray energy sweep is performed while satisfying the fixed Rowland condition at the focal point position F of. Since the intensity of the diffracted X-rays at a certain X-ray energy is stored in the multi-channel analyzer 8, the operation of subtracting the background from the result is performed by the operator 9, and the X
Data for each linear energy is stored in the memory 22. When the measurement result stored in the memory 22 is output after the measurement is completed, a DAFS spectrum as shown in FIG. 6 is obtained.
From this measurement result, the atomic level structural analysis of the sample 6 is performed by data analysis of the vibration of the X-ray diffraction intensity at the X-ray energy higher than the absorption edge of the sample 6. According to the above configuration, the same level as the measurement of the EXAFS in the laboratory system (8
DAFS can be measured with a measurement time of up to 24 hours. As shown in the above structure, the position of the goniometer 5 is fixed, the X-ray energy sweep is performed by changing the X-ray emission point position and the spectroscopic / focusing surface, and the position-sensitive proportional counter is used as an X-ray detector. By using 4, sample 6
Without moving the rotation angle and the position of the X-ray detector,
The intensity of the diffracted X-ray from the sample 6 can be measured together with the background, and the DAFS measurement for simultaneously measuring the X-ray absorption spectrum by the X-ray energy sweep and the diffracted X-ray is realized on a laboratory scale.

[0011]

As described above, according to the present invention, the X-ray emission point, the radius of curvature of the concave diffraction grating of the spectroscopic element, and the focus of the spectroscopic element are always located on the Rowland circle. The position of the X-ray emission point is changed while satisfying the Roland condition of the arrangement. The change of the emission point position of the X-ray changes the emission position of the X-ray emitted from the electron beam incident position of the target by making the deflected electron beam incident on the target. The angle of the spectroscopic element and the radius of curvature of the concave diffraction grating are changed by the spectroscopic element driving means in synchronism with the change of the emission point position of the X-ray. With this configuration, it is possible to fix the position of the goniometer that holds the sample placed at the focusing position of the spectroscopic element. Further, since the change of the emission point of the X-ray is an electric position movement, the X-ray source itself can be fixed in position.
Therefore, while the position of the large and heavy goniometer and the X-ray source, which are difficult to move, and the X-ray source are fixed, the energy sweep of the X-ray incident on the sample is performed while satisfying the Roland condition, and the X-ray diffracted by the sample is Since it is possible to carry out the measurement of the intensity of D., it is possible to carry out the measurement of DAFS on a laboratory scale. (Claim 1) In the above structure, since X-rays are incident on the sample at a converging angle condensed by the spectroscopic element, a position-sensitive X-ray detector is used as an X-ray detector for detecting diffracted light from the sample. By using, the angle information is converted into the position information on the position-sensitive X-ray detector, and the angle scanning by the goniometer can be performed substantially once. Therefore, since the measurement time can be shortened, practical laboratory scale DAFS measurement can be performed without using high intensity X-rays. (Claim 2)

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an X-ray analysis apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a crystal bending mechanism according to an example.

FIG. 3 is a schematic diagram for explaining the operation of spectroscopy / condensing by a monochromator.

FIG. 4 is a graph showing an example of data stored in the multi-channel analyzer according to the example.

FIG. 5 is a schematic diagram illustrating a state of a Rowland circle change due to a change in X-ray emission point position.

FIG. 6 is a graph showing an example of a DAFS spectrum.

FIG. 7 is a schematic diagram showing a schematic configuration of a laboratory EXAFS according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray analyzer 2 ... X-ray source 3 ... Crystal X-ray monochromator (spectroscopic element) 4 ... Position sensitive proportional counter (X-ray detector) 5 ... Goniometer 6 ... Sample 10 ... Controller (spectroscopic element driving means) ) 11 ... Target 14 ... Deflection electrode 16 ... Electron beam 17 ... Crystal bending mechanism (spectral element driving means) 18 ... Rotating stage (spectral element driving means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Wasa 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel Co., Ltd. Kobe Research Laboratory (72) Inventor Koji Inoue Takatsuka, Nishi-ku, Kobe-shi, Hyogo 1-5-5 stand, Kobe Steel, Ltd. Kobe Research Institute

Claims (2)

[Claims] 1. An emission point of X-rays emitted from an X-ray source,
The spectroscopic element that disperses and condenses the X-rays by the concave diffraction grating and the condensing focus of the X-rays by the spectroscopic element are located on the Roland circle having the radius of curvature of the concave diffraction grating as the diameter. In the X-ray analysis apparatus, wherein the X-ray source and the spectroscopic element are arranged, and a goniometer equipped with a sample and an X-ray detector is arranged so that the sample is located at the converging focal point, And an X-ray source for changing the emission point position of the X-ray by changing the incident position of the electron beam incident on the target formed on the cylindrical surface along the circumference, and the emission point position of the X-ray. Of the X-ray incident on the spectroscopic element and the radius of curvature of the concave diffraction grating in synchronism with the change of the spectroscopic element, and the rotation axis for holding the sample does not move on the Rowland circle. X-ray analysis apparatus characterized by comprising; and a deployed goniometer. 2. The X-ray analysis apparatus according to claim 1, wherein the X-ray detector is a position-sensitive X-ray detector.