JP4657506B2 - X-ray spectroscopy method and X-ray spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray spectroscopy method for extracting a parallel X-ray beam using a multilayer mirror having a curved reflecting surface, and to an X-ray spectrometer for the same.
[0002]
[Prior art]
FIG. 15A is a plan view showing a conventional X-ray spectroscopic method for X-ray diffraction measurement of a thin film sample using X-ray beams of two types of wavelengths. For one goniometer 10, a first X-ray spectrometer 12 and a second X-ray spectrometer 14 are prepared. The first X-ray spectrometer 12 extracts a parallel X-ray beam having a first wavelength, a first X-ray source 16 that generates an X-ray having a first wavelength, and a first multilayer film having a curved reflecting surface. And a mirror 18. The curved reflecting surface is formed of a multilayer film having an inclined lattice plane interval, and the cross-sectional shape thereof is a shape along the first parabola. A first X-ray source 16 is disposed at the focal position of the first parabola. The X-rays 20 having the first wavelength generated by the first X-ray source 16 are reflected by the curved reflecting surface of the first multilayer mirror 18 to become a first parallel X-ray beam 22 composed of X-ray bundles parallel to each other. The first parallel X-ray beam 22 is incident on the thin film sample 24 at a low angle, and diffracted X-rays therefrom are detected by the X-ray detector 28 through the solar slit 26. The diffraction pattern of the thin film sample 24 can be obtained by measuring the intensity of the diffracted X-ray while rotating the X-ray detector 28 around the thin film sample 24 while the thin film sample 24 is stationary.
[0003]
Next, to measure the X-ray diffraction of the thin film sample 24 with the X-rays of the second wavelength, the goniometer 10 is moved in parallel to the second X-ray spectrometer 14. Then, the X-ray having the second wavelength generated by the second X-ray source 30 is reflected by the second multilayer mirror 32 to obtain a second parallel X-ray beam 34, which is irradiated onto the thin film sample 24.
[0004]
For example, in the first X-ray spectrometer 12, Cu (copper) is used as a target material of the first X-ray source 16, and CuKα of the characteristic X-ray can be used for diffraction measurement. On the other hand, in the second X-ray spectrometer 14, Cr (chromium) is used as a target material of the second X-ray source 30, and CrKα of the characteristic X-ray can be used for diffraction measurement. In such a case, the first multilayer mirror 18 needs to be a dedicated mirror made for CuKα, and the second multilayer mirror 32 needs to be a dedicated mirror made for CrKα. is there.
[0005]
FIG. 15B is a plan view showing another conventional X-ray spectroscopic method for X-ray diffraction measurement of a thin film sample using X-ray beams of two types of wavelengths. In this conventional example, an X-ray source 36 capable of generating X-rays of two types of wavelengths is used. Then, one of the two types of multilayer mirrors 18 and 32 is selected according to the two types of wavelengths. Whichever wavelength is used, the goniometer 10 may remain in the same position. As the X-ray source 36 for generating X-rays of two types of wavelengths, for example, an X having a rotating counter cathode (so-called zebra type target) in which two types of metals are alternately arranged on the outer peripheral surface of a cylindrical target. A wire tube can be used. When this X-ray source is used, characteristic X-rays attributed to two types of metal are generated at the same time. By selecting one of the two types of multilayer mirrors 18 and 32 according to the wavelength to be extracted, a desired X-ray source can be obtained. Only the characteristic X-rays of the wavelength can be extracted.
[0006]
[Problems to be solved by the invention]
In the conventional X-ray spectroscopy method shown in FIG. 15A, it is necessary to move the goniometer in order to switch the wavelength of X-rays used for measurement, and two sets of X-ray spectrometers must be prepared. . On the other hand, in the X-ray spectroscopic method shown in FIG. 15B, the goniometer does not need to be moved in parallel. However, according to the two types of wavelengths used for the measurement, a multilayer mirror dedicated to the wavelength is separately provided. Must be prepared.
[0007]
The present invention has been made to solve the above-described problems, and the object thereof is not to move the sample and the X-ray source when switching between two kinds of wavelengths, and one kind of multilayer mirror. It is to provide an X-ray spectroscopic method that is sufficient by itself, and to provide an X-ray spectroscopic device that performs the method.
[0008]
[Means for Solving the Problems]
  The X-ray spectroscopic method of the first invention uses a multifocal X-ray source and includes the following steps (a) to (d). (A) A first focal point that generates X-rays having a first wavelength and a second focal point that generates X-rays having a second wavelength are provided. The first focal point and the second focal point when viewed from the X-ray extraction direction. Preparing an X-ray source in a position different from the focal point; (B) A step of preparing a multilayer mirror having a curved reflecting surface made of a multilayer film with inclined lattice plane spacing. (C) The first focal point of the X-ray source is arranged at the focal position of the first parabola based on the first wavelength, and the curved reflecting surface is arranged along the first parabola, and the first parabola is arranged. A first spectroscopic step of extracting a parallel X-ray beam by reflecting X-rays of a first wavelength generated at a focal point by the curved reflecting surface; (D) The second focal point of the X-ray source is arranged at the focal position of the second parabola based on the second wavelength, and the curved reflecting surface is arranged along the second parabola, and the second A second spectroscopic stage for extracting a parallel X-ray beam by reflecting the X-ray of the second wavelength generated at the focal point by the curved reflecting surface, wherein the position and orientation of the X-ray source are the same as in the first spectroscopic stage. Yes, compared with the first spectroscopic stage, the curved reflecting surfaceThe arrangement position of the curved reflecting surface at at least one point is not changed, and only the posture and curvature of the curved reflecting surface are changed, at a position at least partially overlapping with the first spectroscopic stage, and the first spectroscopic stage. In the same direction asA second spectroscopic stage in which a parallel X-ray beam is extracted; This X-ray spectroscopy method can be applied regardless of whether the two types of wavelengths are relatively far apart or close to each other.
[0009]
  The X-ray spectroscopy method of the second invention isThe X-ray source in the first invention is embodied. That is, the X-ray source is a rotating anti-cathode X-ray tube, and a large-diameter portion and a small-diameter portion are alternately arranged in the circumferential direction on the outer peripheral surface of the rotating anti-cathode, and the surface of the large-diameter portion is the first surface. It corresponds to the first focus that generates X-rays of one wavelength, and the surface of the small diameter portion corresponds to the second focus that generates X-rays of the second wavelength.
[0010]
An X-ray spectrometer of the third invention is an apparatus for carrying out the X-ray spectroscopy method of the first invention, and includes the following (a) to (c). (A) A first focal point that generates X-rays having a first wavelength and a second focal point that generates X-rays having a second wavelength are provided. The first focal point and the second focal point when viewed from the X-ray extraction direction. An X-ray source whose focal point is different. (B) a multilayer mirror having a curved reflecting surface composed of a multilayer film with inclined lattice plane spacing, wherein the first posture along a first parabola with the first focal point as a focal position based on the first wavelength; A multilayer mirror that can be selectively disposed in a second posture along a second parabola with the second focal point as a focal position based on a second wavelength. (C) Curvature changing means for changing the curvature of the curved reflecting surface.
[0011]
  The X-ray spectrometer of the fourth invention isThe X-ray source according to the third invention is embodied. That is, the X-ray source is a rotating anti-cathode X-ray tube, and a large-diameter portion and a small-diameter portion are alternately arranged in the circumferential direction on the outer peripheral surface of the rotating anti-cathode, and the surface of the large-diameter portion is the first surface. It corresponds to the first focus that generates X-rays of one wavelength, and the surface of the small diameter portion corresponds to the second focus that generates X-rays of the second wavelength.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
First, the multilayer mirror used in the present invention will be described. FIG. 1A is a cross-sectional view of the multilayer mirror 38. The multilayer mirror 38 is obtained by laminating a multilayer film 42 on the surface of a Si (silicon) substrate 40 having a thickness of 0.5 mm. FIG. 1B is a cross-sectional view schematically showing the multilayer film 42. The multilayer film 42 is formed by alternately stacking 200 layers of W (tungsten) 44 as a heavy element and Si (silicon) 46 as a light element. In this multilayer film 42, the thickness d of one cycle varies depending on the location. For example, the thickness of one cycle at point A is d1, and the thickness of one cycle at point B is d2. From the viewpoint of X-ray diffraction, the thickness d of one period of the multilayer film 42 corresponds to the lattice spacing of the crystal. As described above, the multilayer film in which the thickness d of one period varies depending on the location is “graded grating”. This is referred to as a “plane spacing” multilayer film. When a parallel X-ray beam is extracted using a parabolic curved reflecting surface, a multilayer film having such an inclined lattice plane interval is required.
[0013]
Generally speaking, the multilayer film used in the present invention can be produced under the following conditions. A typical heavy element is W (tungsten). As light elements, Si (silicon), C (carbon), B4C (boron carbide), and the like are conceivable. The number of layers (period number) of heavy elements and light elements can be about 100 to 200 layers. The thickness d for one period is about 3 to 12 nm.
[0014]
Next, the principle of the X-ray spectroscopy method of the present invention will be described. FIG. 2 is an explanatory diagram showing an X-ray optical system for selecting and extracting X-rays having two wavelengths. The focal point of the X-ray source of the Cu target is arranged at the focal position F of the first parabola 48. A first multilayer mirror 50 is disposed along the first parabola 48. The curved reflecting surface of the first multilayer mirror 50 is a parabolic curve formed when a part of the first parabola 48 is translated in a direction perpendicular to the axis 49 of the first parabola 48 (a direction perpendicular to the paper surface). It is a surface. This curved reflecting surface is formed of a multilayer film having an inclined lattice plane interval as shown in FIG. The first parabola 48 is a parabola for diffracting CuKα rays that are characteristic X-rays of Cu.
[0015]
There are an infinite number of parabolas that share the focal point F and the axis, but a parabola that diffracts CuKα rays can be obtained as follows. Considering the case of using a multilayer mirror as shown in FIG. 1B, when the period d of the multilayer film and the wavelength λ of X-rays (the wavelength of CuKα rays) are determined, the diffraction phenomenon is based on Bragg's law. Is determined. Then, if it is determined that the nearest end of the multilayer mirror (the end closest to the X-ray source; this is C point) is arranged at a position about 80 mm from the X-ray source, the spatial position of the C point is determined. When the focal position F, the axis, and the point C are determined, the first parabola 48 is uniquely determined. Since the X-ray incident angle θ on the parabola changes according to the distance X (distance in the axial direction from the apex of the parabola), the period d of the multilayer mirror 50 is continuously changed according to the change of the incident angle θ. This allows Bragg's law to be satisfied at any position on the parabola. In this embodiment, the length of the multilayer mirror 50 is about 40 mm.
[0016]
Next, consider placing the X-ray source of the Cr target at the same focal position F as the above-mentioned Cu target. In this case, the wavelength of the CrKα ray that is the specific X-ray of Cr is different from the wavelength of the CuKα ray described above. Therefore, since the X-ray incident angles satisfying Bragg's law are different, it is necessary to use a second parabola 52 different from the first parabola 48. The second parabola 52 is a parabola that diffracts CrKα rays. The second multilayer mirror 54 is curved along the second parabola 52. Of course, the curvature of the first multilayer mirror 50 is different from that of the second multilayer mirror 54.
[0017]
The area indicated by hatching in FIG. 2 is an area occupied by incident X-rays to the multilayer mirror and outgoing X-rays from the multilayer mirror. The outgoing X-ray is a parallel beam composed of X-ray bundles parallel to each other.
[0018]
Next, a condition for arranging the two multilayer mirrors 50 and 54 at the same position is considered. When the first parabola 48 and the first multilayer mirror 50 are moved upward by a distance G between the points C and D (G = 2.25 mm in this embodiment), the first multilayer mirror 50 Of the second multilayer mirror 54 is overlapped with the closest point D of the second multilayer mirror 54. The state after movement is shown in FIG. The first parabola 48 and its axis 49 are indicated by broken lines.
[0019]
  For example, by arranging the X-ray source of the Cu target at the focal position F1 of the first parabola 48 and arranging the first multilayer mirror 50 along the first parabola 48, the width in the Y direction can be increased. A 1.19 mm parallel X-ray beam is obtained. In addition, an X-ray source of a Cr target is arranged at the focal position F2 of the second parabola 52, and the second parabola 52 is arranged along the second parabola 52.2By arranging the multilayer mirror 54, a parallel X-ray beam having a width in the Y direction of 1.69 mm can be obtained.
[0020]
Next, consider common use of the two multilayer mirrors 50 and 54. In FIG. 3, if the first multilayer mirror 50 is a variable-curvature mirror, it can be curved along the first parabola 48 or curved along the second parabola 52. However, since the cycle d of the multilayer film of the first multilayer mirror 50 continuously changes so as to reflect the CuKα ray, even if only the curvature is changed along the second parabola 52, the cycle Since d does not change so as to reflect the CrKα ray, it does not strictly satisfy Bragg's law for the CrKα ray at all points of the multilayer mirror 50. Therefore, the error is examined.
[0021]
An X-ray incident angle at each point in the second multilayer mirror 54 having an ideal period d along the second parabola 52 is defined as θ1. On the other hand, the first multilayer mirror 50 is bent along the second parabola 52, and X-ray incidence is performed such that CrKα rays are diffracted according to the period d of each point of the first multilayer mirror 50. Let the angle be θ2. FIG. 12 shows the calculation result of the angle error between θ1 and θ2. The angular error in the range from the nearest end (distance X = 80 mm) to the farthest end (distance X = 120 mm) of the multilayer mirror was 0.0086 to 0.0077 degrees. That is, the angle error is less than 0.01 degrees. On the other hand, the half width of the reflection peak by the multilayer mirror is about 0.05 degree. Therefore, even if there is an angle deviation of less than 0.01 degree with respect to the ideal incident angle, this is considerably smaller than the half-value width of the multilayer mirror. A beam can be obtained. The X-ray intensity is about 90% with respect to the ideal state, and the intensity is not so lowered, and it is sufficiently usable. Based on the above examination results, it was found that the multilayer mirror having the tilt period d designed for CuKα rays can be used as a multilayer mirror for CrKα rays only by changing the curvature.
[0022]
Next, the remaining problem is to prepare an X-ray source that separately generates characteristic X-rays of Cu and Cr from two close focal points F1 and F2 as shown in FIG. Hereinafter, such a multifocal X-ray source will be described.
[0023]
First, a conventional X-ray tube capable of generating different characteristic X-rays will be described. FIG. 5 shows a conventional zebra-type rotating counter cathode. Cu target 56 and Cr target 58 are alternately arranged along the circumferential direction. When the rotating cathode 64 is irradiated with the electron beam 62 from the filament 60, the X-ray from the Cu target 56 and the X-ray from the Cr target 58 are mixed and extracted as an X-ray beam 66. In this case, when viewed from the X-ray extraction direction, X-rays from the Cu target 56 and X-rays from the Cr target 58 are generated from the same focal position. This cannot be used for the application shown in FIG.
[0024]
Next, a multifocal rotary anti-cathode X-ray tube used in the present invention will be described. In FIG. 6, a plurality of annular grooves 70 are provided in parallel on the outer peripheral surface of the rotating counter cathode 68. The rotating counter cathode 68 has a cup-shaped Cr base 71 (internally water-cooled) coated with an outer layer 72 made of Cu. Then, by processing the groove 70 deeper than the thickness of the outer layer 72, Cr, which is the material of the base 71, is exposed on the bottom surface of the groove 70. As a method for coating the outer layer 72, diffusion bonding, vapor deposition, or the like is used.
[0025]
FIG. 8A is a side view of the rotating counter cathode 68 of FIG. 6 (the left half is a cross-sectional view). The outer diameter of the cylindrical rotating counter cathode 68 is 100 mm. The depth of the groove 70 is the same as the distance G in FIG. 3 and is 2.25 mm. The width of the groove 70 is 2 mm. FIG. 8B shows the shape of the focal point as viewed from the X-ray extraction direction. The X-ray 74 generated from the surface (Cu) of the outer layer 72 and the X-ray 76 generated from the bottom surface (Cr) of the groove 70 are separated by a distance G. By the way, since the groove 70 is annular, the X-rays 74 and 76 have a portion 78 in which no X-rays are generated in the longitudinal direction of the cross section.
[0026]
Therefore, in order to eliminate such a defect, the groove 70a is formed in a spiral shape in the rotating counter cathode 68a of FIG. FIG. 8C is a side view of the rotating counter cathode 68a of FIG. 7 (the left half is a cross-sectional view). The depth G of the groove 70a is 2.25 mm, and the width is 2 mm. FIG. 8D shows the shape of the focal point as viewed from the X-ray extraction direction in that case. In this case, by rotating the rotating counter cathode 68a, the X-rays 74a and 76a can obtain uniform X-ray intensity in the longitudinal direction of the cross section.
[0027]
As another manufacturing method, the entire rotating counter cathode may be manufactured with Cu in a shape as shown in FIG. 8C, and then Cr may be deposited only on the bottom surface of the groove 70a.
[0028]
FIG. 9 shows another example of a multifocal rotating counter cathode. FIG. 9A is a cross-sectional view (a cross-sectional view perpendicular to the rotation axis) showing a state during the production of the rotating anti-cathode. In this rotating counter cathode, first, a Cu outer layer 72b is coated on the outer peripheral surface of a cup-shaped Cr base 71b. Next, as shown in FIG. 9B, the outer peripheral surface is processed at three locations in the circumferential direction to expose Cr. As a result, the large diameter portions 78 and the small diameter portions 80 are alternately arranged in the circumferential direction. The hem 84 of the large diameter portion 78 is cut in the tangential direction so that the large diameter portion 78 does not get in the way when the X-rays from the small diameter portion 80 are taken out in the direction of the arrow 82. When the electron beam hits the large-diameter portion 78, a characteristic X-ray of Cu is generated, and when the electron beam hits the small-diameter portion 80, a characteristic X-ray of Cr is generated. FIG. 9C is a side sectional view of the rotating counter cathode of FIG. 9B. The difference in radius between the large diameter portion 78 and the small diameter portion 80 is G, which is the same as the groove depth G in FIG. FIG. 9D shows the shape of the focal point as viewed from the X-ray extraction direction. The focus shape is the same as that in FIG. It may be divided into n equal parts other than 3 (n = positive integer).
[0029]
By using a multifocal type rotary anti-cathode X-ray tube as shown in FIGS. 8C and 9C, the position and orientation of the X-ray tube are not changed at all, as shown in FIG. It becomes possible to extract X-rays of two types of wavelengths from different focal positions.
[0030]
Next, the multilayer mirror 50 used in FIG. 3 will be described in detail. FIG. 10 is a plan view showing an outer shape curve of the multilayer mirror 50. In this multilayer mirror, one end (left end in the figure) of the substrate constituting the mirror is fixed to the wall surface, and a point H (right end in the figure) is used as a free end to apply a load to bend the substrate. It is. U is the distance from the wall (left end in FIG. 10), and V is the distance from the center in the width direction of the substrate (1/2 of the width). When the outer shape curve 86 of the substrate is represented by the expression (1) in FIG. 16 (this point will be described later), a paraboloid surface in which the curved surface of the substrate reflects the CuKα line when a load W is applied to the tip. Become.
[0031]
Next, a procedure for obtaining the outer curve 86 will be described. First, a first parabola 48 (see FIG. 2) that reflects the CuKα ray is obtained, and its radius of curvature R1 (which varies depending on the distance X in FIG. 2) is calculated. Next, the curvature radius of the substrate (cantilever) is calculated using equation (2) in FIG. That is, in the equation (2) in FIG. 16, the parameters a, b, and W are changed, and the radius of curvature at each position of the reflection area to be used (40 mm × 20 mm, the area shown by hatching in FIG. 10) is calculated. . Optimum a, b, and W are obtained so that this curvature radius matches the curvature radius R1 as much as possible. Thereby, the numerical value of a in each distance U is obtained. When the numerical value a (corresponding to V in FIG. 10) is approximated by a function of a quintic equation of the distance U, the equation (1) in FIG. 16 is obtained. If this mathematical formula is set in an NC-controlled machine tool, the external curve 86 can be machined. When a load W is applied to the tip of the multilayer mirror, at least a portion of the reflection region (40 mm × 20 mm) is curved along the first parabola 48. The amount of displacement of the tip from the planar state at that time is 0.25 mm.
[0032]
If the above-mentioned curvature R1 is changed to the curvature R2 for CrKα line and a mathematical expression corresponding to the expression (1) in FIG. 16 is obtained, the outer shape curve of the multilayer mirror for CrKα line can be obtained. When this is compared with the external curve 86 for CuKα line, the error is about 10 μm at the maximum, which is within the range of the processing error. Therefore, there is no practical difference even if the same outer shape curve is used for the multilayer mirror for CuKα rays and the multilayer mirror for CrKα rays.
[0033]
FIG. 11 is a perspective view showing an example of a mechanism for changing the curvature of the multilayer mirror. The base end of the multilayer mirror 50 is fixed to a fixed base 88. The tip of the multilayer mirror 50 is pushed up by a push rod 90. By adjusting the load applied to the push rod 90 (actually adjusting the displacement of the push rod 90), the curvature of the curved surface (which becomes a paraboloid) of the multilayer mirror 50 can be changed. In FIG. 11, a multilayer film is formed on the side where the mirror 50 is curved (the upper side in FIG. 11). The moving mechanism of the push rod 90 and the fixed base 88 are attached to the rotary base 92. When the turntable 92 is rotated around its center line 94, the posture (attachment angle) of the multilayer mirror 50 with respect to the X-ray source can be changed.
[0034]
The mechanism for changing the curvature of the multilayer mirror is not limited to that shown in FIG. For example, a method in which the multilayer mirror is curved by pushing each other from both ends in the longitudinal direction toward the center, or the upper surface of the multilayer mirror is supported by four rods and both ends of the multilayer mirror are pushed up by push rods from below. A bending method (four-point bending method) or the like may be employed.
[0035]
FIG. 4 is an explanatory view showing an operation of bending the multilayer mirror shown in FIG. 10 so as to follow a desired parabola 96. To place the multilayer mirror 50 along the parabola 96, first, the point J at the base end of the multilayer mirror 50 is placed on the parabola 96. Next, by rotating the turntable 92 of FIG. 11, the inclination of the multilayer mirror 50 at the point J is matched with the inclination of the parabola 96. Next, the point H at the tip of the multilayer mirror 50 is pushed in the direction of the arrow 82 so that the point H is on the parabola 96. Thus, the curved surface of the multilayer mirror 50 becomes a paraboloid along the parabola 96. The length of the multilayer mirror 50 is 65 mm, but the range actually used is a range where the distance X from the X-ray source is about 80 to 120 mm.
[0036]
Next, an example of how to use this X-ray spectrometer will be described. In FIG. 3, as the X-ray source, an X-ray tube having a multifocal rotating counter cathode 68a shown in FIG. 8C is used. Further, as the first multilayer mirror 50, the multilayer mirror shown in FIG. 10 is used. First, the X-ray tube is positioned so that the Cu focus of the rotating anti-cathode is at the focus position F1 and the Cr focus is at the focus position F2. Next, the first multilayer mirror 50 is bent along the first parabola 48 in the work procedure shown in FIG. When X-rays are generated from the X-ray tube in this state, CuKα rays generated from the focal position F1 are reflected by the first multilayer mirror 50 and taken out as a parallel X-ray beam to the right in FIG. . Using this CuKα ray, for example, X-ray diffraction measurement of a thin film sample is performed. Since the CrKα ray generated from the focal position F2 does not satisfy Bragg's law even when it hits the first multilayer mirror 50, the CrKα ray does not come out of this X-ray spectrometer.
[0037]
  Next, the X-ray spectrometer is changed so as to extract CrKα rays. The X-ray tube may be in the same position and posture, and only the posture (tilt angle) and curvature of the first multilayer mirror 50 are changed. That is, the first multilayer mirror 50 is inclined and curved along the second parabola 52.The arrangement position of the point J at the base end of the first multilayer mirror 50 is in the same arrangement position in the first spectral stage for extracting CuKα rays and the second spectral stage for extracting CrKα rays. That is, the arrangement position of the curved reflecting surface at at least one point (point J) of the curved reflecting surface of the multilayer mirror is not changed in the second spectroscopic stage as compared with the first spectroscopic stage.In this case, instead of using the second multilayer mirror 54 for CrKα rays, the first multilayer mirror 50 is used as it is, and its inclination and curvature are changed along the second parabola 52. At this time, the displacement from the planar state at the tip of the first multilayer mirror 50 (point H in FIG. 10) is 0.28 mm. By the way, since the amount of displacement from the planar state at the tip when bent for CuKα rays was 0.25 mm as described above, the displacement of the tip of the multilayer mirror when changing from CuKα rays to CrKα rays. The amount will be increased by 0.03 mm.
[0038]
  In this case, an angle error as shown in FIG. 12 occurs as compared with the case where the original second multilayer mirror 54 is used, but this angle error is within the allowable range as described above. When X-rays are generated from the X-ray tube in this state, the CrKα rays generated from the focal position F2 are reflected by the multilayer mirror curved along the second parabola 52 to become a parallel X-ray beam. 3 is taken out to the right. Since the first CuKα ray extraction position and extraction direction and the next CrKα ray extraction position and extraction direction are substantially the same as viewed from the sample, X-rays of two wavelengths are used without changing the sample position. Can be measured.As shown in FIG. 3, in the first spectroscopic stage for extracting the CuKα ray from the focal point F1 and the second spectroscopic stage for extracting the CrKα ray from the focal point F2, the positions of the parallel beams to be extracted at least partially overlap each other. The parallel beams are extracted in the same direction.
[0039]
In the above description, a combination of CuKα rays and CrKα rays is used as the two types of wavelengths, but other combinations may be used. For example, a combination of CuKα rays and CuKβ rays can also be applied. In that case, a multifocal rotating counter cathode may be made by using only Cu as the material. A rotating counter cathode used in this case is shown in FIG. FIG. 17A is a side view of such a rotating counter cathode (the left half is a cross-sectional view). The width Q of the groove is 6 mm, and the width P of the mountain is 6 mm. FIG. 17B is an enlarged view of the S part in FIG. The depth G of the groove is 0.45 mm. In the case of the combination of the CuKα ray and the CrKα ray, the position of the multilayer mirror can be made the same by setting the distance G in FIG. 3 to 0.45 mm. In this rotating anti-cathode, the thickness t of the anti-cathode is uniform in both the crest and the groove as shown in FIG. That is, the thickness t is set to 2 mm in any part. As a result, the thickness can be made as thin and uniform as possible, and the cooling efficiency of the rotating cathode can be increased.
[0040]
In the above description, a multilayer mirror having a cycle d for CuKα rays is made and used as a multilayer mirror for CrKα rays. However, the cycle d for CuKα rays and the cycle for CrKα rays are used. A multilayer mirror having a period d in the middle of d may be made, and this may be used for both the CuKα line and the CrKα line.
[0041]
  next,As a reference example,Another type of X-ray spectroscopic method (a type using a single focus type X-ray source) will be described. FIG. 13 is an explanatory view showing the principle of an X-ray spectroscopic method using a single-focus X-ray source. The following two points are greatly different from the X-ray spectroscopy method of FIG. The first difference is that X-rays of two wavelengths are generated from the same focal position F. The second difference is that when changing the wavelength, in addition to changing the attitude (tilt angle) and curvature of the multilayer mirror, the mounting position is also shifted. The same multilayer mirror is used for the two wavelengths as in FIG. This type of X-ray spectroscopy is effective when the two wavelengths are very close. If the two wavelengths are separated, the extraction positions of the X-ray beams having the two wavelengths extracted from the multilayer mirror are separated from each other, and therefore cannot be applied. If the two wavelengths are relatively far apart, the X-ray spectroscopy method of FIG. 3 will be used.
[0042]
In FIG. 13, a first parabola 98 is a parabola that reflects a CuKα ray that is one of characteristic X-rays of a Cu target. The second parabola 100 is a parabola that reflects CuKβ rays, which are another characteristic X-ray of the Cu target. The multilayer mirror 102 is a mirror (shown in FIG. 10) designed to reflect CuKα rays, and is also commonly used for CuKβ rays.
[0043]
In FIG. 13, when taking out CuKα rays, the multilayer mirror 102 is curved along the first parabola 98. Then, the parallel X-ray beam taken out from the multilayer mirror 102 is finally narrowed out by the exit slit 104 and finally taken out. That is, the parallel X-ray beam coming out of the multilayer mirror 102 is in the range of the width M, but is finally extracted by narrowing it down with the opening width of the exit slit 104.
[0044]
Next, when taking out CuKβ rays, the multilayer mirror 102 is moved along the second parabola 100 after the closest end of the multilayer mirror 102 is shifted from the point D to the point C so as to be placed on the second parabola 100. Rotate and bend. In this case, the parallel X-ray beam extracted from the multilayer mirror 102 is in the range of the width N, but is also finally extracted after being narrowed down by the opening width of the exit slit 104. Therefore, the exit slit 104 is designed to take out a region where the parallel X-ray beam of CuKα rays and the parallel X-ray beam of CuKβ rays overlap each other. In this embodiment, the opening width of the exit slit 104 is 0.5 mm. By using this exit slit 104, the CuKα line and the CuKβ line are extracted at the same extraction position and extraction direction as viewed from the sample. Therefore, it is possible to separately measure both the CuKα ray and the CuKβ ray while keeping the position of the sample the same.
[0045]
In FIG. 13, when CuKα rays and CuKβ rays are taken out separately, the focal position of the X-ray source may be the same, so an ordinary Cu target X-ray tube can be used. The position and posture of this X-ray tube may always remain the same.
[0046]
FIG. 14 is a graph showing the spectral characteristics of the X-ray spectrometer of FIG. This graph is a diffraction pattern obtained by angle-spectralizing a parallel X-ray beam extracted using the X-ray spectrometer shown in FIG. 13 using a crystal monochromator made of Si (004). The horizontal axis represents the diffraction angle (2θ) by the Si (004) monochromator, and the vertical axis represents the intensity of the diffracted X-ray (unit: cps). A curve indicated by a solid line is a spectral pattern of CuKβ rays taken out by the X-ray spectrometer of FIG. 13, and a curve indicated by a broken line is a spectral pattern of CuKα rays. In the curve shown by the solid line, CuKα1 and CuKα2 appear slightly in addition to the peak of the CuKβ line, but this is an intensity that can be ignored in practice. As described above, according to this spectroscopic method, it is possible to separately extract CuKα rays and CuKβ rays using the same multilayer mirror.
[0047]
As an example of performing X-ray analysis using CuKα rays and CuKβ rays, the following cases are conceivable. When accurately determining the lattice constant of a sample using CuKα rays, the wavelengths of CuKα1 and CuKα2 rays overlap and the ratio changes within the measurement angle range for samples that require low-angle reflection measurement. To do. In such a case, an advanced technique is required to obtain an accurate lattice constant. For such a sample, it is possible to measure the lattice constant accurately by measuring the low-angle reflection with CuKβ rays. According to the present invention, the wavelength of the X-ray can be switched by simply changing the curvature of the same multilayer mirror without moving the X-ray source and without moving the position of the sample. Quick measurement.
[0048]
【The invention's effect】
In the X-ray spectroscopy method and apparatus of the present invention, it is not necessary to move the sample and the X-ray source when switching between two types of wavelengths, and only one type of multilayer mirror is sufficient.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a multilayer mirror used in the present invention.
FIG. 2 is an explanatory diagram showing an X-ray optical system for selecting and extracting X-rays of two wavelengths.
FIG. 3 is an explanatory diagram showing an X-ray spectroscopy method for separately extracting X-rays of two wavelengths using a multifocal X-ray source.
4 is an explanatory diagram showing an operation of bending the multilayer mirror shown in FIG. 10 so as to follow a desired parabola. FIG.
FIG. 5 is a perspective view of a conventional zebra-type rotating counter cathode.
FIG. 6 is a perspective view showing a part of a rotating counter cathode in which a plurality of annular grooves are provided in parallel on the outer peripheral surface in a cutaway manner.
FIG. 7 is a perspective view showing a part of a rotating counter cathode provided with a spiral groove on the outer peripheral surface in a cutaway manner.
8A is a partial cross-sectional side view of the rotating anti-cathode of FIG. 6, FIG. 8B is a focal shape of the rotating anti-cathode of FIG. 6, and FIG. 8C is a partial cross-sectional side view of the rotating anti-cathode of FIG. (D) is a focus shape of the rotating anti-cathode of FIG.
FIG. 9 is a plan sectional view, a side sectional view, and a focal shape of another example of a multifocal rotating counter cathode.
FIG. 10 is a plan view of a multilayer mirror used in the present invention.
FIG. 11 is a perspective view showing an example of a mechanism for changing the curvature of the multilayer mirror.
FIG. 12 is a graph showing an angular error when the same multilayer mirror is used for two wavelengths.
FIG. 13 is an explanatory diagram showing the principle of a type of X-ray spectroscopic method using a single-focus X-ray source.
14 is a graph showing spectral characteristics of the X-ray spectrometer of FIG.
FIG. 15 is a plan view showing a conventional X-ray spectroscopy method for X-ray diffraction measurement of a thin film sample using X-ray beams of two types of wavelengths.
FIG. 16 is a mathematical formula showing an outer shape curve of a multilayer mirror and a mathematical formula for obtaining a radius of curvature.
17A is a partial cross-sectional side view of a rotating counter cathode used when a combination of CuKα line and CrKα line is used, and FIG. 17B is an enlarged view of an S part in FIG.
[Explanation of symbols]
48 First parabola
50 First multilayer mirror
52 Second Parabola
54 Second multilayer mirror
68 Rotating anti-cathode
70 groove
71 base
72 outer layer

Claims (4)

An X-ray spectroscopy method comprising the following steps (a) to (d):
(A) A first focal point that generates X-rays having a first wavelength and a second focal point that generates X-rays having a second wavelength are provided. The first focal point and the second focal point when viewed from the X-ray extraction direction. Preparing an X-ray source in a position different from the focal point;
(B) A step of preparing a multilayer mirror having a curved reflecting surface made of a multilayer film with inclined lattice plane spacing.
(C) The first focal point of the X-ray source is arranged at the focal position of the first parabola based on the first wavelength, and the curved reflecting surface is arranged along the first parabola, and the first parabola is arranged. A first spectroscopic step of extracting a parallel X-ray beam by reflecting X-rays of a first wavelength generated at a focal point by the curved reflecting surface;
(D) The second focal point of the X-ray source is arranged at the focal position of the second parabola based on the second wavelength, and the curved reflecting surface is arranged along the second parabola, and the second A second spectroscopic stage for extracting a parallel X-ray beam by reflecting the X-ray of the second wavelength generated at the focal point by the curved reflecting surface, wherein the position and orientation of the X-ray source are the same as in the first spectroscopic stage. And, in comparison with the first spectroscopic step, the position and the curvature of the curved reflecting surface are changed without changing the arrangement position of the curved reflecting surface at at least one point of the curved reflecting surface, and the first spectroscopic step. A second spectral stage in which a parallel X-ray beam is extracted at a position at least partially overlapping with the first spectral stage in the same direction . 2. The X-ray spectroscopy method according to claim 1, wherein the X-ray source is a rotating counter-cathode X-ray tube, and a large-diameter portion and a small-diameter portion are alternately arranged in the circumferential direction on the outer peripheral surface of the rotating counter-cathode. The surface of the large-diameter portion corresponds to the first focus that generates the X-rays of the first wavelength, and the surface of the small-diameter portion corresponds to the second focus that generates the X-rays of the second wavelength. An X-ray spectroscopy method characterized by the above. An X-ray spectrometer comprising the following (a) to (c).
(A) A first focal point that generates X-rays having a first wavelength and a second focal point that generates X-rays having a second wavelength are provided. The first focal point and the second focal point when viewed from the X-ray extraction direction. An X-ray source whose focal point is different.
(B) a multilayer mirror having a curved reflecting surface composed of a multilayer film with inclined lattice plane spacing, wherein the first posture along a first parabola with the first focal point as a focal position based on the first wavelength; A multilayer mirror that can be selectively disposed in a second posture along a second parabola with the second focal point as a focal position based on a second wavelength.
(C) Curvature changing means for changing the curvature of the curved reflecting surface. 4. The X-ray spectrometer according to claim 3, wherein the X-ray source is a rotating anti-cathode X-ray tube, and a large-diameter portion and a small-diameter portion are alternately arranged in the circumferential direction on the outer peripheral surface of the rotating anti-cathode. The surface of the large-diameter portion corresponds to the first focus that generates the X-rays of the first wavelength, and the surface of the small-diameter portion corresponds to the second focus that generates the X-rays of the second wavelength. An X-ray spectrometer characterized by that.

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