JP2007163219A - Fluorescence x-ray analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescence X-ray analyzer capable of suppressing the generation of higher-order diffracted X rays or escape peaks and to accurately and precisely perform analysis. <P>SOLUTION: The fluorescent X-ray analyzer is equipped with an X-ray source 1 for irradiating a sample S with primary X rays 2, a multilayered film spectral element 3, of which the periodic length for spectrally diffracting the fluorescent X rays 4 emitted from the sample S is 1-2 nm and which is characterized in that the roughness σ of the boundary surface 34 of the reflecting layer and a spacer layer is 20% or higher, with respect to the periodic length and a detector 5 for measuring the intensities of the fluorescent X rays 4 that have been spectrally diffracted by the multilayer film spectral element 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-order diffracted X-ray and an escape peak in a fluorescent X-ray analyzer that separates a fluorescent X-ray generated from a sample irradiated with a primary X-ray generated from an X-ray source with a multilayer film spectroscopic element. The present invention relates to an apparatus that can suppress the occurrence.

  When fluorescent X-rays generated from a sample irradiated with primary X-rays generated from an X-ray source are dispersed with a multilayer spectroscopic element, not only the primary diffraction X-rays but also the second, third, fourth, etc. And higher-order diffracted X-rays are diffracted by the spectroscopic element, and escape peaks due to the higher-order diffracted X-rays and higher-order diffracted X-rays overlap with and separate from the fluorescent X-ray that is the analysis line of the analysis target element. Qualitative analysis and quantitative analysis may be difficult.

  For example, in the case of analyzing a copper alloy sample, the higher-order ray is a fluorescent X-ray of an element contained in the sample by the irradiated energy from the sample irradiated with the primary X-ray from the X-ray source, that is, the sample Fluorescent X-rays of copper (Cu) as a main component are generated and incident on a germanium crystal as a spectroscopic element, and diffracted X-rays such as first, second, third, and fourth orders are generated by spectroscopy of the germanium crystal. . This second or higher order diffracted X-ray is referred to as a higher order line.

The escape peak is, for example, an Ar-Kα absorption edge energy (3.20 keV) if the X-ray detector is a proportional counter using P-10 gas containing 10% argon (Ar) gas as a detection gas. ) And a peak obtained by subtracting the Ar-Kα ray energy (2.96 keV) from the fluorescence X-ray energy. For example, the fluorescent X-ray energy of 4.01keV of Ca-Kβ ₁ line in the X-ray detector is incident, escape peaks of Ca-Kβ ₁ line is 4.01-2.96 = 1.05keV. An escape peak also occurs when higher-order diffracted X-rays enter the proportional counter, which is an X-ray detector.

In such a case, there is a method of suppressing higher-order diffracted X-rays using a multilayer spectroscopic element and a total reflection mirror (see Patent Document 1). An apparatus for suppressing higher-order diffracted X-rays using two multilayered film spectroscopic elements, a multilayered film spectroscopic element for suppressing even-order diffracted X-rays and a multilayered film spectroscopic element for suppressing odd-order diffracted X-rays (See Patent Document 2).
JP-A-5-52778 JP-A-8-327567

  However, in such a fluorescent X-ray analysis method and apparatus, since the multilayer spectroscopic element, the total reflection mirror, and a plurality of multilayer spectroscopic elements are used, the optical system of the apparatus is complicated, the optical path length is long, and the reflection of the optical system The efficiency is lowered and the intensity of the first-order diffracted X-ray is reduced.

  Therefore, in the present invention, the occurrence of escape peaks due to higher-order diffracted X-rays and higher-order diffracted X-rays is suppressed without losing the intensity of the first-order diffracted X-rays using a single crystal, and qualitative analysis or An object of the present invention is to provide a fluorescent X-ray analyzer capable of performing quantitative analysis accurately and accurately.

  In order to achieve the above object, an X-ray fluorescence analyzer according to the configuration of the present invention is configured by laminating a number of layer pairs composed of an X-ray source for irradiating a sample with primary X-rays, a reflective layer and a spacer layer. In the fluorescent X-ray analysis apparatus, comprising the multilayer film spectroscopic element that separates the fluorescent X-rays generated from the sample, and a detector that measures the intensity of the fluorescent X-ray dispersed by the multilayer film spectroscopic element, the multilayer film The periodic length of the spectroscopic element is 1 to 2 nanometers (nm), and the roughness of the boundary surface between the reflective layer and the spacer layer is 20% or more of the periodic length.

  According to the apparatus of the configuration of the present invention, the multilayer spectral element has a period length of 1 to 2 nm, and the roughness of the boundary surface between the reflective layer and the spacer layer is 20% or more of the period length with respect to the period length. Because it is configured, the third-order diffracted X-ray intensity is 5% or less of the first-order diffracted X-ray intensity, suppressing the occurrence of escape peaks due to higher-order diffracted X-rays and higher-order diffracted X-rays, A spectrum overlapping with the fluorescent X-ray that is the analysis line of the analysis target element does not occur, and qualitative analysis and quantitative analysis can be performed accurately and accurately. Here, the roughness of the boundary surface between the reflective layer and the spacer layer with respect to the periodic length is preferably 40% or less of the periodic length, the reflective layer of the multilayer spectral element is made of tungsten, and the spacer layer is carbonized. More preferably, it is made of boron.

  The X-ray fluorescence analyzer according to the first embodiment of the present invention will be described below with reference to FIG. The sample S is configured by laminating a large number of layer pairs composed of an X-ray source 1 such as an X-ray tube that irradiates the primary X-ray 2 and a reflective layer and a spacer layer, and the periodic length d is 1.5 nm. The roughness σ of the boundary surface between the reflective layer and the spacer layer is 0.45 nm with respect to the periodic length d, and the multilayer spectral element 3 that splits the fluorescent X-rays 4 generated from the sample S and the multilayer spectral element 3 are spectrally separated. The X-ray fluorescence analyzer 10 includes a detector 5 that measures the intensity of the fluorescent X-ray 4.

As shown in FIG. 2, the multilayer spectroscopic element 3 uses tungsten (W) for the reflective layer 31 and boron carbide (B ₄ C) for the spacer layer 32, and the film thickness ratio between the reflective layer 31 and the spacer layer 32. Is configured 1: 1. As shown in FIG. 3 which is an enlarged view of a single layer pair of the multilayer spectral element 3, the roughness σ of the boundary surface 34 constituted by the reflective layer 31 and the spacer layer 32 is 0.45 nm, and the periodic length d is 1. As shown in FIG. 2, the layer pair 35 having a thickness of 5 nm is formed by laminating 150 layers to 300 layers on the substrate 7 which is a silicon wafer by ion beam sputtering deposition. That is, the roughness σ of the boundary surface 34 is configured to be 30% with respect to the period length d.

  FIG. 4 shows the results of measuring higher-order diffraction X-ray intensities such as first-order diffraction X-ray intensity, second-order diffraction X-ray intensity, and third-order diffraction X-ray intensity diffracted by the multilayer spectroscopic element. FIG. 4 is a relative intensity curve of the diffracted X-ray expressed with the order of the diffracted X-ray as the horizontal axis and the relative intensity between the first-order diffracted X-ray intensity and the higher-order diffracted X-ray intensity as the vertical axis. The intensity curve 41 and the roughness σ of the boundary surface 34 of the multilayer spectroscopic element in which the roughness σ of the surface 34 is configured to be 0.45 nm, the periodic length d is configured to 1.5 nm, and the roughness σ is configured to be 30% of the periodic length d. An intensity curve 42 of the multilayer spectroscopic element in which the periodic length d is configured to be 1.5 nm and the roughness σ is configured to be 20% of the periodic length d is shown at 0.3 nm. In the multilayer spectroscopic elements having the intensity curves 41 and 42, the thickness ratio of the reflective layer to the spacer layer is 1: 1, and 300 layers are laminated.

  According to the measurement result of FIG. 4, the multilayer spectroscopic element of the first embodiment in which the roughness σ of the boundary surface 34 is set to 30% with respect to the period length d has a secondary diffraction X-ray intensity of 7%. The next diffraction X-ray intensity is 0.1% or less. In the case of a multilayer spectroscopic element in which the roughness σ of the boundary surface 34 is set to 20% with respect to the period length d, the second-order diffraction X-ray intensity is 30% with respect to the first-order diffraction X-ray intensity, and the third-order The diffracted X-ray has an intensity of 5% or less. According to this measurement result, in order to suppress higher-order diffracted X-rays, it can be understood that the ratio of the roughness σ of the boundary surface 34 to the period length d should be 20% or more. If the roughness σ value of the boundary surface 34 is increased and the ratio with respect to the period length d is increased too much, the primary diffraction X-ray intensity also decreases. Therefore, it is preferable to set the roughness σ of the boundary surface 34 to 40% or less of the periodic length d.

  In the first embodiment, the period length d is configured to 1.5 nm, but in order to obtain sufficient diffraction X-ray intensity of the multilayer spectral element and to set the ratio of roughness σ to the period length d to 20 to 40%, The period length d is preferably 1 to 2 nm. In conventional multilayer spectroscopic elements, the periodic length d is 7 to 15 nm, the roughness σ of the boundary surface 34 is often about 0.3 nm, and the ratio of the roughness σ to the periodic length d is about 2 to 4%. . FIG. 4 shows an intensity curve 43 of a conventional multilayer spectroscopic element in which the period length d is 15 nm and the roughness σ of the boundary surface 34 is 0.3 nm. The relative intensity of the second-order diffracted X-ray is 1 It is about 90% of the next diffraction X-ray intensity, the relative intensity of the third diffraction X-ray is about 70%, and the generation of higher-order diffraction X-rays is not suppressed.

  As described above, in the X-ray fluorescence analyzer 10 according to the first embodiment, in the multilayer spectroscopic element 3 that splits the fluorescent X-rays 4 generated from the sample S irradiated with the primary X-rays 2 from the X-ray source 1. Since the generation of high-order diffraction X-rays is sufficiently suppressed as shown by the intensity curve 41 in FIG. 4, the generation of escape peaks due to high-order diffraction X-rays is also suppressed, and the analysis line of the analysis target element A spectrum overlapping with a certain fluorescent X-ray does not occur, and the analysis can be performed accurately and accurately.

  In the first embodiment, the reflective layer is tungsten, the spacer layer is boron carbide, the film thickness ratio is 1: 1, and the multilayer spectroscopic element is formed by stacking 300 layers by ion beam sputtering. Not limited to the configuration, the reflective layer is made of molybdenum, lanthanum, nickel, etc., the spacer layer is made of carbon, etc., and the film thickness ratio is 1: 2 or 1: 3, and the layers are laminated in 100 to 400 layers. can do.

  Next, a fluorescent X-ray analyzer according to the second embodiment will be described. First, the configuration of this apparatus will be described with reference to FIG. Multilayer film spectroscopic element that is configured by laminating a number of layer pairs composed of a reflective layer and a spacer layer and radiating fluorescent X-rays 4 generated from the sample S. 3, a detector 5 that measures the intensity of the secondary X-ray 4 dispersed by the multilayer spectroscopic element 3, and the multilayer spectroscopic element 3 so that the wavelength of the fluorescent X-ray 4 incident on the detector 5 changes. Linking means 7 that links the detector 5 with each other, that is, a so-called goniometer, a qualitative analysis means 13, a quantitative analysis means 14, a semi-quantitative analysis means 15, and a display means 16 for displaying analysis conditions and analysis results. X-ray analyzer 20. The multilayer spectroscopic element 3 is the same as that in the first embodiment.

  When the fluorescent X-ray 4 is incident on the multilayer spectroscopic element 3 at a certain incident angle θ, the extension line 9 of the fluorescent X-ray 4 and the fluorescent X-ray 6 dispersed by the multilayer spectroscopic element 3 are twice the incident angle θ. The interlocking means 7, that is, the goniometer, changes the wavelength of the fluorescent X-ray 6 that is split by changing the spectral angle 2θ, while the spectral X-ray 6 is incident on the detector 5. In order to continue, the multilayer spectroscopic element 3 is rotated around an axis O perpendicular to the paper surface passing through the center of the surface, and the detector 5 is made a circle 12 around the axis O by twice the rotation angle. Rotate along. This operation is a goniometer scan of the fluorescent X-ray analyzer. In the interlocking means 7, for example, the incident angle θ and the spectral angle 2θ formed as a result of the rotation of the multilayer film spectroscopic element 3 and the detector 5 are confirmed by a potentiometer or the like attached to the axis O.

  By continuously interlocking the multilayer film spectroscopic element 3 and the detector 5 with the interlocking means 7, the fluorescent X-rays 4 generated from the sample S are spectrally separated into respective wavelengths and detected. As a result, a spectrum indicating the intensity of the fluorescent X-ray 6 at each spectral angle 2θ is obtained based on the signal related to the spectral angle 2θ from the interlocking means 7 and the signal related to the intensity of the fluorescent X-ray 6 from the detector 5. Qualitative, quantitative or semi-quantitative analysis is performed by the analyzing means 13, quantitative analyzing means 14 or semi-quantitative analyzing means 15, and the result is displayed on the display means 16.

  Next, a method for semi-quantitative analysis of phosphorus (P) in a copper alloy will be described as an operation of the fluorescent X-ray analyzer of the second embodiment. First, for comparison, a semi-quantitative analysis using a conventional fluorescent X-ray analyzer in which a goniometer spectroscopic element is composed of germanium crystals (Ge) will be described. A copper alloy, which is a sample, is placed on a sample stage, set to predetermined semi-quantitative analysis conditions, a goniometer is scanned to perform semi-quantitative analysis, and the analysis result is displayed on the display means. Semi-quantitative analysis is an analysis that determines the content of an element in a sample based on the intensity of the spectral peak of a qualitative chart obtained by scanning a goniometer in the vicinity of the analysis line of the target element. Used when no quantitative value is required.

  Copper alloy samples A and B having a known phosphorus content are used so that the effects of the present invention can be easily understood. In the vicinity of P-Kα (2.01 keV) which is an analytical line of phosphorus for two samples of a copper alloy sample A having a phosphorus content of 0 mass% and a copper alloy sample B having a phosphorus content of 0.035 mass% FIG. 8 shows a qualitative chart obtained by performing a qualitative analysis by scanning a goniometer. In FIG. 8, the horizontal axis represents X-ray energy, and the vertical axis represents the X-ray intensity detected by the detector. When FIG. 8 is seen, the spectrum peak is detected in the position of the P-Kα line, which is the analytical line of phosphorus, in both samples A and B. Judging from this qualitative chart, sample A also contains phosphorus. Become. As described above, when qualitative analysis or semi-quantitative analysis of phosphorus in a copper alloy is performed with a conventional apparatus, an erroneous analysis result that the sample A having a phosphorus content of 0 mass% contains phosphorus is generated.

  This is because, as described above, when a copper alloy is analyzed, a Cu-Kα higher-order line is generated, the energy of the quaternary line therein is 2.01 keV, and the P-Kα line which is a phosphorus analysis line Because it overlaps with.

  Like the sample A, the spectral peak of the sample B overlaps with the Cu-Kα quaternary line, and when the obtained qualitative chart is analyzed as it is, the value becomes higher than the true phosphorus content of the sample B and an inaccurate half It becomes a quantitative analysis result.

  Using the X-ray fluorescence analyzer of the second embodiment, qualitative results obtained by scanning the vicinity of phosphorus P-Kα (2.01 keV) for copper alloy samples A and B as in the case of using the conventional apparatus. A chart is shown in FIG. In FIG. 6, the multilayer spectroscopic element 3 of the X-ray fluorescence spectrometer of the second embodiment is indicated as RX25. Looking at this qualitative chart, in the copper alloy sample A in which the phosphorus content is 0 mass%, no spectral peak is detected at a position adjacent to P-Kα (2.01 keV) of phosphorus. That is, when the semi-quantitative analysis of phosphorus in a copper alloy is performed using the fluorescent X-ray analyzer of the second embodiment, the fourth-order diffracted X-ray of the Cu—Kα ray detected by the conventional apparatus is detected. Since no peak is detected, there is no erroneous analysis result that the copper alloy sample A having a phosphorus content of 0 mass% contains phosphorus. In addition, Cu-Kα quaternary peak does not overlap for sample B, and accurate semi-quantitative analysis can be performed.

  In order to perform semi-quantitative analysis of an unknown sample using the fluorescent X-ray analyzer according to the second embodiment, a qualitative chart is obtained by scanning a goniometer in the vicinity of the analysis line of the element to be analyzed as in the case of the known sample. By acquiring, the content of the element to be analyzed in the unknown sample may be obtained by a known semi-quantitative analysis method.

  Next, as the operation of the fluorescent X-ray analyzer of the second embodiment, a method for semi-quantitative analysis of aluminum in barium titanate is compared with the result of conventional semi-quantitative analysis in the same manner as the analysis of phosphorus in copper alloy. While explaining. As in the copper alloy sample analysis, the barium titanate sample C containing no aluminum is used so that the effect of the present invention can be easily understood. Using a conventional fluorescent X-ray analyzer using a PET crystal as a spectroscopic element of a goniometer, Al-Kα (1.49 keV), which is an aluminum analysis line, of a barium titanate sample C having an aluminum content of 0 mass% FIG. 9 shows a qualitative chart obtained by performing a qualitative analysis by scanning a goniometer in the vicinity. In FIG. 9, as in FIG. 8, the horizontal axis represents the energy of X-rays, and the vertical axis represents the X-ray intensity detected by the detector. Referring to FIG. 9, a spectrum peak is detected at the position of Al—Kα of aluminum, and judging from this qualitative chart, sample C contains aluminum.

  As described above, when qualitative analysis or semi-quantitative analysis of aluminum in barium titanate is performed by a conventional apparatus, an erroneous analysis result that sample C having aluminum content of 0 mass% contains aluminum is produced.

  As in the analysis of the copper alloy, the fluorescent X-ray of barium (Ba), which is the main component of the sample C, which is barium titanate, is incident on the PET crystal as the spectroscopic element, and is separated by the PET crystal. This is because an escape peak is generated together with a Ba-Lα tertiary line having an energy of 4.466 keV and overlaps with an Al-Kα line which is an analysis line of 1.49 keV aluminum.

  Using the fluorescent X-ray analysis apparatus of the second embodiment, a goniometer is used in the vicinity of an Al-Kα line (1.49 keV), which is an aluminum analysis line, for the barium titanate sample C as in the case of using the conventional apparatus. FIG. 7 shows a qualitative chart obtained by performing a qualitative analysis by scanning. In FIG. 7, the multilayer spectroscopic element 3 of the X-ray fluorescence spectrometer of the second embodiment is indicated as RX25. Looking at this qualitative chart, in the barium titanate sample C in which the aluminum content is 0 mass%, no spectral peak is detected at a position adjacent to the vicinity of the Al-Kα line (1.49 keV). That is, when semi-quantitative analysis of aluminum in barium titanate is performed using the fluorescent X-ray analyzer of the second embodiment, the Ba-Lα tertiary line detected by the conventional apparatus and its escape peak are detected. Is not detected, so that an erroneous analysis result that aluminum is contained in the barium titanate sample C in which the aluminum content is 0 mass% does not occur.

  As described above, when the fluorescent X-ray analyzer of the second embodiment is used, higher-order diffracted X-rays are suppressed, so that accurate and accurate analysis can be performed.

1 is a schematic diagram showing a fluorescent X-ray analysis apparatus according to a first embodiment of the present invention. It is sectional drawing which shows the multilayer film spectroscopic element of an analyzer same as the above. It is sectional drawing which shows 1 layer pair of a multilayer film spectroscopy element same as the above. It is a figure which shows an example of the relative intensity curve of a high-order diffraction X-ray. It is the schematic which shows the fluorescent-X-ray-analysis apparatus of 2nd Embodiment of this invention. It is a qualitative chart of a copper alloy using the analyzer same as the above. It is a qualitative chart of barium titanate using the analyzer same as the above. It is a qualitative chart of a copper alloy using a conventional fluorescent X-ray analyzer. It is a qualitative chart of barium titanate using the analyzer same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray source 2 Primary X-ray 3 Multilayer film | membrane spectroscopy element 4 Secondary X-ray 5 Detector 6 Fluorescence X-rays 10 and 20 Fluorescence X-ray analyzer 31 Reflective layer 32 Spacer layer 34 Boundary surface S Sample d Period length σ Roughness

Claims (2)

An X-ray source for irradiating the sample with primary X-rays;
A multilayer film spectroscopic element that is configured by laminating a large number of layer pairs each including a reflective layer and a spacer layer, and that separates fluorescent X-rays generated from a sample;
In a fluorescent X-ray analyzer equipped with a detector for measuring the intensity of fluorescent X-rays dispersed by the multilayer spectroscopic element,
X-ray fluorescence analysis characterized in that the periodic length of the multilayer spectroscopic element is 1 to 2 nm, and the roughness of the boundary surface between the reflective layer and the spacer layer is 20% or more of the periodic length with respect to the periodic length apparatus. In claim 1,
A fluorescent X-ray analysis apparatus in which the reflective layer is made of tungsten and the spacer layer is made of boron carbide.

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