JPH1019809A - Fluorescent x-ray analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent X-ray analyzer capable of achieving fluorescent X-ray analysis of light elements at S/N ratio and of simultaneously measuring heavy elements. SOLUTION: An emitting opening for emitting X rays from an X-ray source 1 without damping is provided in the X-ray source 1, and also charged particle removing means is provided between the X-ray source 1 and a sample 7, and further an orbit of the X rays is kept in a vacuum. Thereby, even X rays of characteristics of low energy can be incident on the sample 7 without damping strength, and charged particles which are a cause of reduction in S/N ratio are not advanced in the device. Further, detecting means of fluorescent X rays is constructed by comprising high energy area detecting means and low energy area detecting means, whereby all energy areas can be concurrently detected and accordingly light elements and heavy elements can be concurrently measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluorescence analyzer for analyzing elements on the surface of a sample by detecting X-ray fluorescence generated when the X-ray generated by an X-ray source is incident on the sample. About.

[0002]

2. Description of the Related Art In the field of semiconductors, a small amount of impurities on the surface may have a great effect on the performance as devices become more highly integrated. Therefore, in order to detect the above-mentioned trace impurities, a trace trace element analysis and evaluation technique is regarded as important. As one of the analysis / evaluation techniques, there is a technique using X-rays, and a typical one is a fluorescent X-ray analysis technique. This is to analyze trace elements on the surface of a sample by detecting fluorescent X-rays generated by irradiating the sample with X-rays generated by an X-ray source.
FIG. 5 shows a configuration example of a conventional X-ray fluorescence analyzer. The X-ray 37 emitted from the X-ray source 31 passes through a beryllium window (not shown) provided in the X-ray source 31, is shaped by a slit 32, and is incident on a sample 34 via a spectral crystal 33. The constituent elements on the sample 34 excited by the incident X-rays are fluorescent X-rays each having a specific energy (wavelength).
The emitted fluorescent X-rays 38 are detected by an X-ray detector 35. The X-ray detector 35 converts the intensity of the incident fluorescent X-ray into a voltage pulse corresponding to the energy and outputs the voltage pulse to the signal processing circuit 36. The signal processing circuit 36 measures the intensity of each fluorescent X-ray energy by counting the voltage pulse for each wave height, thereby performing a quantitative analysis of a trace element on the sample 34. Here, the X-rays used to excite the above elements consist of continuous X-rays and characteristic X-rays.
In particular, the characteristic X-rays described above are used to excite trace elements. This is because, as shown in FIG. 6, the characteristic X-ray has higher intensity and higher excitation efficiency than the continuous X-ray. The energy (wavelength) and intensity of the characteristic X-ray differ depending on the substance of the target material provided in the X-ray source for generating the X-ray. Further, as the energy of the incident X-ray (characteristic X-ray in this case) is closer to the excitation energy (absorption edge energy) of the target element, the fluorescence efficiency is higher, so that the target material can be properly used depending on the target element. Done.

[0003]

However, the conventional X-ray fluorescence analyzer has the following problems. In the case of a light element, the energy of the characteristic X-ray used for excitation is low due to its low absorption edge energy, and the intensity of the characteristic X-ray is low due to attenuation when passing through the beryllium window of the X-ray source. Therefore, it takes time to obtain a sufficient signal amount with high accuracy, and therefore, it has been practically impossible to analyze a trace amount of light elements. Therefore, it is conceivable to increase the transmittance by thinning the beryllium window. However, scattered electrons emitted simultaneously with the X-rays from the target material pass through the beryllium window and become a background noise source, so that the detection signal is reduced. However, there was a problem that the S / N ratio was lowered. In many cases, a semiconductor detector is used as the X-ray detector 35. However, since a low energy X-ray is greatly attenuated by a beryllium window installed in the detector, the semiconductor detector is light. Detection of elemental signals is not possible. When a proportional counter having a spectroscopic element and a thin X-ray incident window is used instead of the semiconductor detector, a light element and a heavy element (mainly a K-ray ) May be difficult to measure. The present invention has been made in view of the above circumstances, and it is an object of the present invention to realize a fluorescent X-ray analysis of a light element with a high S / N ratio and at the same time, a heavy element can be measured. An object of the present invention is to provide an X-ray analyzer.

[0004]

In order to achieve the above object, the present invention provides a method for detecting fluorescent X-rays, which is generated by irradiating a sample with X-rays generated by an X-ray source. In an X-ray fluorescence spectrometer for analyzing elements on a sample surface, an X-ray source is provided with an emission opening for emitting X-rays from the X-ray source without attenuation, and a charge is provided between the X-ray source and the sample. A fluorescent particle, wherein a particle removing means is provided, and the orbit of the X-ray is maintained in a vacuum.
It is configured as a line analyzer. In order to more efficiently remove charged particles, the charged particle removing means may be provided immediately after the X-ray source. Further, the charged particle removing means can be constituted by an electrode which deflects and adsorbs the trajectory of the scattered electrons. Further, the charged particle removing means may be constituted by a magnetic field generating means for deflecting the trajectory of the scattered electrons and an electrode for adsorbing the scattered electrons. Further, by configuring the detection means to include the high energy area detection means and the low energy area detection means, it is possible to simultaneously detect all energy areas. Furthermore, a semiconductor detector can be used as the high energy region detecting means, and a spectroscopic element and a proportional counter can be used as the low energy region detecting means. Further, by providing the proportional counter with an entrance window made of a polymer, it is possible to efficiently detect low-energy fluorescent X-rays.

[0005]

The X-ray fluorescence spectrometer according to the present invention comprises:
Since the emission opening for emitting X-rays without attenuation from the X-ray source is provided, even low-energy characteristic X-rays can be emitted without attenuating the intensity. Further, the above X
Since the charged particle removing means is provided between the radiation source and the sample, charged particles which are emitted simultaneously with the X-rays from the emission aperture and cause a reduction in the S / N ratio do not enter the apparatus. Furthermore, since the X-ray orbit is kept in a vacuum,
There is no attenuation of X-rays by air. In addition, the charged particle removing means constituted by an electrode which deflects and adsorbs the trajectory of the scattered electrons or a magnetic field generating means which deflects the trajectory of the scattered electrons and the electrode which adsorbs the scattered electrons is provided immediately after the X-ray source. By installing the device at a location, charged particles can be efficiently removed. In addition, since the detecting means is provided with the high-energy area detecting means and the low-energy area detecting means, it is possible to simultaneously detect all energy areas, and thus to measure light and heavy elements simultaneously. It becomes possible.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to facilitate understanding of the present invention. The following embodiments and examples are mere examples embodying the present invention, and do not limit the technical scope of the present invention. FIG. 1 is a diagram showing a schematic configuration of an X-ray fluorescence spectrometer according to an embodiment of the present invention, FIG. 2 is a diagram showing a schematic configuration of a low energy region detecting means and a detection method, and FIG. FIG. 4 is a diagram showing a schematic configuration of the means, and FIG. 4 is a spectrum diagram showing a measurement result obtained by a fluorescent X-ray analyzer according to the embodiment of the present invention. The X-ray fluorescence analyzer according to the present embodiment is configured as shown in FIG. The rotating anti-cathode type X-ray source 1 does not have a transmission film such as a beryllium window. Therefore, the X-ray emitted from the X-ray source 1 without attenuation of intensity passes between the pair of electrode plates 2 for generating an electric field so as to be orthogonal to the traveling direction of the X-ray. Here, the trajectory of the scattered electrons emitted together with the X-rays from the X-ray source 1 is deflected and disappears by hitting the electrode plate 2 (details will be described later). On the other hand, the above X
The line travels without being affected by the electric field, is shaped by the vertical slit 3 and the horizontal slit 4, is collected by the mirror 5 installed on the installation stage 6, and enters the sample 7. The sample 7 is fixed on a gonio stage 8 whose angle can be freely adjusted. The fluorescent X-rays generated by the X-rays incident on the sample 7 are converted into a parallel X-ray flux by passing through a solar slit 9 in which a large number of thin metal plates are stacked in parallel at regular intervals. Among them, the fluorescent X-rays in the low energy region are separated by the artificial multilayered flat plate element 10 made of tungsten and silicon, and detected by the position-sensitive proportional counter detector 11.
In addition, the proportional counter detector 11 is provided with a window 11a made of a thin polymer film having a high transmittance in order to efficiently detect low-energy fluorescent X-rays (see FIG. 2).
In addition, the fluorescent X-rays in the high energy region are transmitted to the semiconductor detector 1
2 is detected. The signal detected by the proportional counter detector 11 and the semiconductor detector 12 is subjected to pulse shaping and pulse height analysis by a signal processor 13 so that a sample 7 is obtained.
Quantitative analysis of the above elements is performed. Further, a vacuum exhaust device 15 is connected to the X-ray source 1, and the inside thereof is kept at a vacuum. Further, the electrode plate 2, the slits 3,..., The proportional counter detector 11, the semiconductor detector 12, and the like, which are provided on the orbit of the X-rays emitted from the X-ray source 1, are all vacuum as shown in FIG. It is housed in a vacuum chamber 17 connected to an exhaust device 16. Further, the X-ray source 1 and the vacuum chamber 1
7 is connected by a vacuum duct 18 as shown in FIG. 3 and is shut off by the gate valve 14 except during measurement.

Next, a method for treating scattered electrons by the electrode plate 2 will be described. As described above, since the X-ray source 1 does not have a means for blocking scattered electrons such as a beryllium window, scattered electrons as well as X-rays can freely enter the apparatus as it is. The scattered electrons have a high energy of several tens keV, and collide with the wall surface inside the device to generate background noise, thereby causing problems such as lowering the S / N ratio. Therefore, in the apparatus according to the present embodiment, as shown in FIG. 3, a pair of electrode plates 2 is installed immediately after the X-ray source, that is, at the entrance of the vacuum chamber 17, and an electric field is generated to generate the scattered electrons. Is deflected to collide with the electrode plate 2 and disappear. As shown in FIG. 3, the electrode plates 2 are arranged at the same interval as the inner diameter of the vacuum duct 18. By applying an appropriate voltage to the electrode plate 2, the trajectory of the scattered electrons is largely bent toward the positive electrode. . At this time, there is no effect on the X-ray orbit. Furthermore, by making the length of the electrode plate 2 sufficiently long in the direction in which the scattered electrons travel, all the scattered electrons whose trajectory has been bent collide with the surface of the positive electrode and disappear as current. Therefore, the scattered electrons do not enter the apparatus and cause no harm, and the trajectory and intensity of the X-rays are not affected.

FIG. 4 shows an example of a spectrum measured by the above apparatus configuration. The signals measured by the proportional counter detector 11 and the semiconductor detector 12 are transmitted to the signal processor 1.
The correction process and the background process by the calibration of the detection sensitivity between the two detectors are performed by 3 and the signals obtained by the different detectors are displayed on the same spectrum display screen. As described above, in the X-ray fluorescence spectrometer according to the present embodiment, the X-ray source 1 is not provided with a beryllium window or the like that causes attenuation of X-rays. Since all are kept in a vacuum, there is no X-ray attenuation by air. Therefore, only the slits 3 and 4 and the mirror 5 physically attenuate the X-rays before the X-rays enter the sample 7. A device that physically attenuates the fluorescent X-rays before the fluorescent X-rays generated from the sample 7 enter the proportional counter detector 11 and the semiconductor detector 12 includes a solar slit 9, a flat plate element 10, Only the entrance window attached to the detector. Further, an extremely thin polymer film is used for the entrance window of the proportional counter detector 11 for detecting fluorescent X-rays in a low energy region. Therefore, the measurement can be performed without greatly attenuating the X-rays emitted from the X-ray source 1 and the fluorescent X-rays emitted from the sample 7, so that analysis for a trace amount of light elements can be performed. It is possible.
Further, the X-ray is emitted from the X-ray source 1 at the same time as the
Since the diffused electrons that cause the reduction in the ratio are all eliminated immediately after the X-ray source 1, they do not jump into the apparatus and perform high-precision measurement without lowering the S / N ratio. be able to. Furthermore, by using the flat plate element 10 as the low energy region detecting means and the proportional counter detector 11 and the semiconductor detector 12 as the high energy region detecting means together, the light element and the heavy element can be simultaneously analyzed. Is possible.

[0009]

In the above embodiment, a pair of electrode plates 2 is used as a means for removing scattered electrons, and the trajectory of the scattered electrons is deflected by generating an electric field, and the scattered electrons collide with the electrode plate 2 and disappear. However, a magnetic field may be used in place of an electric field as a means for deflecting the orbit of the scattered electrons. That is,
An electric field generator such as an electromagnet may be provided in place of the electrode plate 2 to deflect the trajectory of the scattered electrons and cause the scattered electrons to disappear by colliding with a separately provided electrode plate.

[0010]

As described above, according to the present invention,
An X-ray fluorescence spectrometer capable of realizing X-ray fluorescence analysis of light elements at a high S / N ratio and simultaneously measuring heavy elements can be provided.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a schematic configuration of a low-energy region detecting means and a detecting method.

FIG. 3 is a diagram showing a schematic configuration of a charged particle removing unit.

FIG. 4 is a spectrum diagram showing measurement results obtained by a fluorescent X-ray analyzer according to the embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a conventional fluorescent X-ray analyzer.

FIG. 6 is a wavelength distribution diagram of X-rays.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray source 2 ... Electrode plate 3 ... Vertical slit 4 ... Horizontal slit 5 ... Mirror 6 ... Installation stage 7 ... Sample 8 ... Gonio stage 9 ... Solar slit 10 ... Plate element 11 ... Proportional counter detector 11a ... High Molecular film 12 Semiconductor detector 13 Signal processor 14 Gate valve 15 Vacuum exhaust device 16 Vacuum exhaust device 17 Vacuum chamber 18 Vacuum duct

Claims (7)

[Claims] 1. An X-ray fluorescence analyzer for analyzing elements on the surface of a sample by detecting X-rays of fluorescence generated by irradiating the sample with X-rays generated by an X-ray source. An X-ray source is provided with an emission opening for emitting X-rays from the X-ray source without attenuation, charged particle removing means is provided between the X-ray source and the sample, and a vacuum is applied on the X-ray orbit. X-ray fluorescence spectrometer, characterized in that it is kept at a minimum. 2. The X-ray fluorescence analyzer according to claim 1, wherein said charged particle removing means is provided immediately after said X-ray source. 3. The X-ray fluorescence analyzer according to claim 1, wherein said charged particle removing means comprises an electrode which deflects and adsorbs the trajectory of the scattered electrons. 4. The X-ray fluorescence analyzer according to claim 1, wherein said charged particle removing means comprises a magnetic field generating means for deflecting the trajectory of the scattered electrons, and an electrode for adsorbing said scattered electrons. 5. The X-ray fluorescence analyzer according to claim 1, wherein said detecting means comprises high-energy area detecting means and low-energy area detecting means. 6. An X-ray fluorescence analyzer according to claim 5, wherein said high energy region detecting means is a semiconductor detector, and said low energy region detecting means is a spectroscopic element and a proportional counter. 7. The X-ray fluorescence spectrometer according to claim 6, wherein the proportional counter has an entrance window made of a polymer.