JP2006337301A - X-ray analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve detection sensitivity and wavelength resolution, by simple modification in an existing wavelength dispersive X-ray analyzer using a Johansson type X-ray spectroscope. <P>SOLUTION: A curved crystal arranged on a Rowland circle 5 is substituted with a plane crystal 6, and a point/parallel type multicapillary X-ray lens 4 is interposed between a sample 2 and the plane crystal 6 to provide a point focal point in an incident end face side and to emit a parallel beam in an emission end face side. A characteristic X-ray emitted from a micro area 3 on the sample 2 in response to irradiation of an electron beam is collected efficiently by the X-ray lens 4 to be converted into a parallel beam, and the X-rays of the same wavelength are diffracted by the plane crystal 6 to be brought into a parallel beam, and is analyzed by an X-ray detector 8. A conventional mechanism of fixing the micro area 3, and of moving the plane crystal 6 and the X-ray detector 8 along the Rowland circle 5 may be used, as it is, in wavelength scanning. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an X-ray spectrometer, and more particularly to a wavelength dispersion type X-ray analyzer suitable for analyzing a minute region, such as an electron beam probe minute analyzer (EPMA) or a scanning electron microscope (SEM). .

  The electron beam probe microanalyzer (EPMA) irradiates a sample with an electron beam with a small diameter having high energy as an excitation ray, and thereby the intrinsic electron emitted to the outside when the inner electrons of the components contained in the sample are excited. By analyzing X-rays, elements are identified and quantified, and the distribution of elements is examined. In addition, the scanning electron microscope (SEM) generally detects secondary electrons and reflected electrons generated from the irradiation position of the electron beam, but recently, an X-ray analysis has been made by adding a wavelength dispersive X-ray spectrometer. A device that enables this is also being developed.

  In this type of X-ray analysis apparatus, a configuration as shown in FIG. 4 has been widely used in the past in order to efficiently disperse intrinsic X-rays emitted from a minute region that can be regarded as almost one point on a sample surface (for example, (See Patent Document 1). In this X-ray analysis apparatus, a minute region 3 irradiated with an electron beam on a sample 2, a Johansson-type curved crystal 10, and an X-ray detector 8 are placed on a Roland circle 5 on the same reference plane (the drawing sheet). The curved crystal 10 and the X-ray detector 8 are moved along the Roland circle 5 by a moving means (not shown) such as a link mechanism with the minute region 3 on the sample 2 as a fixed point. Since the spectral wavelength is determined by the positions of the curved crystal 10 and the X-ray detector 8, the wavelength scanning is performed by the movement thereof, and the type of element is specified.

In general, X-ray spectrometers using spectral crystals as described above have relatively good wavelength resolution, but curved crystals have limitations in the dimensional accuracy of the curved surface, and wavelength resolution obtained with current equipment. Is on the order of 10 ⁻³ . In addition, among the X-rays emitted from the sample 2, only a part of the X-rays that are incident on the curved crystal and are analyzed, and there is a limit to increasing the diffractive surface of the curved crystal. It's not high enough. In recent years, there is a strong demand to perform analysis with higher wavelength resolution or higher detection sensitivity using the existing EPMA and SEM having the above-described configuration.

  Of course, according to the X-ray analyzer (for example, see Patent Document 2) employing an optical path configuration different from the above configuration, there is a possibility that the wavelength resolution and the detection sensitivity can be improved. However, in such an X-ray analysis apparatus, the movement mechanism of the curved crystal 10 and the X-ray detector 8 is completely different during wavelength scanning, so it is necessary to purchase a new apparatus, and a simple modification of an existing apparatus. Etc. can not cope.

Japanese Patent Laid-Open No. 9-236697 JP 2003-294659 A

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to make use of the main configuration of the spectrometer of the existing wavelength dispersion type X-ray analyzer to detect detection sensitivity, wavelength resolution, etc. It is to provide an X-ray analyzer capable of improving the performance.

The first invention made to solve the above problems is an X-ray source that emits X-rays, a spectral crystal that wavelength-disperses the X-rays, and an X-ray detector that detects wavelength-dispersed X-rays, In an X-ray analyzer arranged on the same Roland circle,
A multicapillary, wherein the spectral crystal is a flat crystal, has a point focal point on the incident end face side facing the X-ray source, and emits substantially parallel light on the outgoing end face side between the flat crystal and the X-ray source An X-ray lens is provided.

Further, the second invention made to solve the above problems includes an X-ray source that emits X-rays, a spectral crystal that wavelength-disperses the X-rays, and an X-ray detector that detects wavelength-dispersed X-rays. In the X-ray analyzer arranged on the same Roland circle,
A multicapillary X-ray lens is provided between the X-ray source and the spectroscopic crystal, having a point focal point on the incident end face side facing the X-ray source and emitting substantially parallel light on the exit end face side. The crystal is a curved crystal having a diffractive surface having a curved shape corresponding to the spread angle of the outgoing X-ray by the multicapillary X-ray lens.

  For example, in an X-ray analyzer that irradiates a sample with an excitation beam and performs spectroscopic analysis of X-rays emitted from the sample, such as an electron probe microanalyzer, the X-ray source is the sample itself, and more strictly In other words, the portion of the sample irradiated with the excitation beam and its vicinity.

  In the X-ray analyzers according to the first and second inventions, preferably, the incident end face of the lens is brought close to the sample surface until the point focal point of the multicapillary X-ray lens comes to the sample surface. Thereby, the multicapillary X-ray lens can efficiently capture X-rays emitted from a minute region on the sample with a large solid angle on the incident end face side. The taken-in X-rays are collimated by a multicapillary X-ray lens, and are irradiated to a plate crystal in the X-ray analyzer according to the first invention and to a curved crystal in the X-ray analyzer according to the second invention.

  In the X-ray analyzer according to the first aspect of the invention, X-rays that are parallel beam bundles hit a plate crystal, and X-rays having the same wavelength are diffracted as parallel beam bundles in the same direction and reach the X-ray detector to be detected. Since the X-ray source, the plate crystal, and the X-ray detector are arranged on the same Roland circle, for example, the position of the X-ray source is fixed and the plate crystal and the X-ray are fixed as in the conventional Johansson type X-ray spectrometer. The wavelength of the X-ray to be detected may be scanned by moving the source along the Roland circle. By using a multi-capillary X-ray lens, the utilization efficiency of X-rays can be increased without increasing the diffraction plane of the flat crystal, thereby improving detection sensitivity. In addition, the parallelism of the X-ray flux incident on the flat crystal is high, and the flat crystal can more easily ensure the mechanical accuracy of the diffraction surface than the curved crystal, so that the wavelength resolution can be improved.

  Therefore, according to the X-ray analyzer of the first invention, the Johansson-type curved crystal is replaced with a plate crystal compared to the existing (that is, conventional) wavelength-dispersive X-ray analyzer equipped with the Johansson-type X-ray spectrometer. By inserting a multicapillary X-ray lens between the sample and the flat crystal, the detection mechanism and the wavelength resolution can be improved by using the drive mechanism for wavelength scanning as it is.

  As described above, although the outgoing X-ray flux of the multicapillary X-ray lens has a fairly high parallelism, in principle, a perfect parallel flux cannot be obtained, and it proceeds while spreading slightly with an opening angle. The X-ray analyzer according to the second invention takes into account the spread of the emitted X-ray flux, and X-rays hitting a curved crystal having a diffractive surface having a radius of curvature larger than the radius of the Roland circle have the same wavelength. As X-rays travel, they are diffracted to converge. Therefore, in front of the detection surface of the X-ray detector, the X-ray of the wavelength to be detected is narrowed compared to the case of the parallel beam bundle as in the first invention, and the width of the slit provided in front of the detector is reduced. By narrowing, it becomes easy to remove X-rays having an undesired wavelength. As a result, wavelength resolution can be further improved and noise can be reduced.

  Of course, in the X-ray analyzer according to the second invention as well, as in the X-ray analyzer according to the first invention, for example, the position of the X-ray source is fixed and the plate crystal and the X-ray source are aligned along the Roland circle. Since the wavelength scanning of the X-ray to be detected can be performed by moving, the Johansson-type curved crystal is made more than this by using the driving mechanism for wavelength scanning in the existing wavelength dispersion type X-ray analyzer as it is. Instead of a curved crystal having a large curvature radius, a multicapillary X-ray lens may be inserted between the sample and the curved crystal.

  EPMA, which is an embodiment of the X-ray analyzer according to the first invention, will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of the EPMA of this embodiment, and FIG. 2 is a schematic configuration diagram of the multicapillary X-ray lens in FIG. In addition, the same code | symbol is attached | subjected about the component same as the component described in FIG. 4 already demonstrated.

  In the EPMA according to this embodiment, the Johanson-type curved crystal 10 is replaced with a flat crystal 6 in the EPMA X-ray spectrometer having the conventional configuration described with reference to FIG. 4, and a multicapillary is interposed between the flat crystal 6 and the sample 2. An X-ray lens 4 is inserted. In the present invention, the micro region 3, the plate crystal 6 and the X-ray detector 8 on the sample 2 which is the X-ray source are arranged on the same Roland circle 5, for example, the plate crystal 6 and the X-ray detector 8 are micro The region 3 can be moved on the Roland circle as a fixed point. The flat crystal 6 is arranged so that its diffraction surface circumscribes the Roland circle 5.

  A multicapillary (sometimes called polycapillary) X-ray lens is basically a bundle of a large number of capillaries (several hundreds to millions) made of borosilicate glass with an inner diameter of 2 to several tens of micrometers. As shown in FIG. 2 (b), the X-rays incident on the inside of one capillary 4a totally reflect the inner peripheral surface of the glass wall at an angle less than the critical angle. However, X-rays are efficiently guided using the principle of proceeding. Here, in the multicapillary X-ray lens 4, each capillary is focused in the center on the incident end face side and has a point focal point F on the outer side, and each capillary is bundled in parallel on the opposite exit end face side. It is a parallel type. Accordingly, as shown in FIG. 2 (a), X-rays emitted from an X-ray source that can be regarded as almost a point can be captured with a large solid angle at the incident side end face, and a parallel X-ray bundle can be emitted from the output side end face. .

  The operation of the EPMA of this embodiment will be described. An electron beam emitted from the electron gun 1 is narrowed down to a very small diameter by an objective lens (not shown) or the like and irradiated onto the sample 2, and a characteristic X-ray excited by the electron beam is emitted from the minute region 3 that is the irradiation region. . The intrinsic X-rays are efficiently collected with a large solid angle by the multicapillary X-ray lens 4, emitted as parallel beam bundles, and irradiated onto the flat crystal 6. Since the flat crystal 6 emits X-rays having different wavelengths at different angles, the X-rays having the same wavelength travel toward the X-ray detector 8 as parallel beam bundles, pass through the slit 7 in front of the X-ray detector 8, and the X-ray detector 8. To reach. As described above, when detecting X-rays having different wavelengths, the plate crystal 6 and the X-ray detector 8 (of course, the slit 7 are also integrally moved) are moved along the Roland circle 5 with the minute region 3 as a fixed point. Let

  In the configuration of this embodiment, as described above, the X-rays having the same wavelength incident on the X-ray detector 8 are ideally parallel bundles. Therefore, to increase the signal intensity, the opening of the slit 7 is widened. It is necessary to keep. This increases the detection sensitivity, but X-rays that are different from the target wavelength, that is, not parallel to the X-ray flux of the target wavelength, can easily reach the X-ray detector 8, which is disadvantageous in increasing the wavelength resolution and noise. It is also disadvantageous. Furthermore, the X-ray beam emitted from the multicapillary X-ray lens 4 is not a perfect parallel beam, but travels while spreading slightly with an opening angle (in principle, the same as the critical angle on the inner wall surface of the capillary). . The spread of the X-ray flux also contributes to a decrease in wavelength resolution.

  Therefore, as a modification of the above embodiment, EPMA which is an embodiment of the X-ray analyzer according to the second invention will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of the EPMA of this embodiment. In addition, the same code | symbol is attached | subjected about the component same as the component described in FIG.1, FIG.2 and FIG.4 already demonstrated.

  The EPMA according to this embodiment is obtained by replacing the flat crystal 6 with the curved crystal 9 in the EPMA X-ray spectrometer having the configuration described in FIG. However, the curved crystal 9 is different from the Johansson-type curved crystal 10 in the conventional configuration shown in FIG. 4, and the curvature radius of the curved diffraction surface 9 a is set larger than the radius of the Roland circle 5. The radius of curvature of the diffractive surface 9a of the curved crystal 9 is determined in consideration of the opening angle of the outgoing X-ray bundle of the multicapillary X-ray lens 4, and is determined so that X-rays of the same wavelength are converged appropriately rather than in parallel. It has been. As a result, as shown in FIG. 3, X-rays having the same wavelength are narrowed before the X-ray detector 8 as compared with the case of FIG. 1, and the signal intensity is ensured even if the opening width of the slit 7 is narrowed. be able to. Thereby, the effect of eliminating X-rays having a wavelength different from the target wavelength is enhanced, and noise factors such as scattered X-rays can be reduced.

  In addition, since the said Example is an example of this invention, even if it changes suitably in the range of the meaning of this invention, correction, or addition, it is natural that it is included in the claim of this application.

The schematic block diagram of EPMA by one Example of 1st invention. The schematic block diagram of the multicapillary X-ray lens in FIG. The schematic block diagram of EPMA by one Example of 2nd invention. The schematic block diagram of the conventional typical EPMA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... Sample 3 ... Micro area | region 4 ... Multicapillary X-ray lens 4a ... Capillary 5 ... Roland circle 6 ... Flat crystal 7 ... Slit 8 ... X-ray detector 9 ... Curved crystal 9a ... Diffraction surface

Claims (2)

In an X-ray analyzer in which an X-ray source that emits X-rays, a spectral crystal that wavelength-disperses X-rays, and an X-ray detector that detects wavelength-dispersed X-rays are arranged on the same Roland circle ,
A multicapillary, wherein the spectral crystal is a flat crystal, has a point focal point on the incident end face side facing the X-ray source, and emits substantially parallel light on the outgoing end face side between the flat crystal and the X-ray source An X-ray analyzer provided with an X-ray lens. In an X-ray analyzer in which an X-ray source that emits X-rays, a spectral crystal that wavelength-disperses X-rays, and an X-ray detector that detects wavelength-dispersed X-rays are arranged on the same Roland circle ,
A multicapillary X-ray lens is provided between the X-ray source and the spectroscopic crystal, having a point focal point on the incident end face side facing the X-ray source and emitting substantially parallel light on the exit end face side. An X-ray analyzer characterized in that the crystal is a curved crystal having a curved diffractive surface according to the spread angle of the X-rays emitted from the multicapillary X-ray lens.

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