JP2991253B2 - X-ray fluorescence spectroscopy method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the detection of fluorescent X-rays emitted from light element impurities in a semiconductor material, and qualitatively knowing the impurities to produce a high quality semiconductor material. The present invention relates to a suitable X-ray fluorescence spectroscopy method and apparatus in a material evaluation technology that can be used.

[0002]

2. Description of the Related Art As is well known, a fluorescent X-ray spectrometer is known as a spectrometer for analyzing the chemical bonding state of elements in a solid material. In this X-ray fluorescence spectrometer, a probe of electrons, ions, light, or the like is incident on a material to be analyzed to excite impurity atoms in the material to emit X-rays (fluorescent X-rays) unique to the impurity atoms. This is an apparatus configured to measure the energy distribution of the fluorescent X-ray.

As incident probes in a conventional X-ray fluorescence spectrometer, (i) an electron beam, (ii) X-rays from an X-ray tube, (iii) ions such as protons, (iv) synchrotron radiation ( Bending electromagnetic light source).

However, the analysis target element is beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), or any other light element whose fluorescent X-ray yield is 1% or less. In the case of (1), there is a problem that the measurement cannot be performed or the measurement is insufficient.

[0005] When (i) an electron beam is used as an incident probe, the electron beam has a large ionization cross-sectional area, so that it can emit a relatively strong fluorescent X-ray, but has a large chemical effect. X-ray fluorescence information on the vicinity of the end cannot be obtained.

[0006] Similarly, (ii) in the case of using X-rays from an X-ray tube, there is no X-ray source having energy capable of efficiently exciting light elements, and as a result, fluorescent X-rays from light elements are measured. It cannot be generated with sufficient strength.

(Iii) In the case of using ions such as protons, the effect of exciting light elements is large, so that fluorescent X-rays of sufficient intensity can be emitted. Cause it to occur. for that reason,
The analysis of the obtained fluorescent X-rays becomes complicated. Furthermore, the chemical effect of the fluorescent X-ray yield near the X-ray absorption edge cannot be observed.

(Iv) In the case of using synchrotron radiation, the excitation efficiency of the synchrotron radiation is low, but the number of photons of the incident light is relatively high at 10 ⁸ to 10 ¹⁰ / s, so that observation is possible. An appropriate amount of fluorescent X-rays can be emitted. However, in order to perform high-resolution X-ray fluorescence spectroscopy required for analyzing the state of chemical bonding, the number of photons cannot provide a sufficient X-ray fluorescence signal intensity for measurement.

As described above, in the conventional X-ray fluorescence spectrometer, it was difficult to analyze the chemical bonding state of the light element by capturing the X-ray of the light element in the solid material. Conventionally, it has been difficult to measure fluorescent X-rays from a dilute gas sample containing C, N, O, etc. as main constituent elements.

On the other hand, in the conventional fluorescent X-ray analysis method,
As a means for spectroscopy and detecting fluorescent X-rays with high resolution,
There is a wavelength dispersion method in which fluorescent X-rays separated using a curved crystal or a concave diffraction grating arranged on a Roland circle are detected by a proportional counter. In an optical system in which a spectral body is placed on a Rowland circle, an arrangement is generally used in which fluorescent X-rays emitted from a sample are once passed through an entrance slit.

In the method using the incident slit, a part of the fluorescent X-ray is blocked at the incident slit to form a fluorescent X-ray beam. Therefore, in this method, the detection efficiency of the fluorescent X-rays decreases. As a result, in this method, it is not possible to disperse fluorescent X-rays from a light element having a small fluorescence yield with a sufficient signal intensity.

On the other hand, an arrangement has been already implemented in which the probe is finely squeezed in order to enhance the detection efficiency, whereby the irradiation position of the probe can be regarded as the entrance slit position.

However, in this improved method, the detector such as a proportional counter and the exit slit must be driven along the Rowland circle, which results in a disadvantage that the configuration of the apparatus becomes large and complicated. There is.

When a proportional counter tube having an entrance window formed from a polymer organic thin film is used in a high vacuum chamber, a method of doubling the entrance window and evacuating the space between the windows has conventionally been used. However, in this case, there is a disadvantage that the detection intensity is weakened because the absorption of X-rays by the window is doubled.

[0015]

As described above, the prior art has a drawback that it is difficult to spectrally and efficiently analyze fluorescent X-rays emitted from light element impurities in a material with high resolution. there were. Further, X-ray fluorescence from a gaseous light element sample which is a dilute material could not be captured.

Therefore, an object of the present invention is to efficiently and with high resolution X-ray fluorescence from light element impurities in a solid material or a gas sample, and to analyze the chemical bonding state of these light elements. It is to be.

[0017]

The object of the present invention is to provide a wavelength-dispersive X-ray fluorescence spectroscopic method and apparatus for measuring the energy distribution of X-ray fluorescence by dispersing X-ray fluorescence emitted from a sample by a diffraction grating. This can be achieved by taking the following measures.

(I) As is well known, an undulator can meander an electron beam by an alternating magnetic field and convert a part of the energy of electrons into photons in a wide range from infrared rays to X-rays. .
Radiated light from the undulator, compared with radiation from the conventional storage ring, 10 ² to a high intensity
10 ³ times quasi-monochromatic radiation. Therefore, by irradiating this light with a light element, it is possible to generate fluorescent X-rays sufficient for measurement.

In such an undulator, undulator radiation light obtained from an apparatus having a number of photons of 10 ¹¹ / s or more is used as an incident probe, and the incident probe irradiates a sample. When the irradiation position on the sample surface is regarded as the light source point, a diffraction grating is provided on the irradiation path of the fluorescent X-ray (incident light) from this light source point. This diffraction grating is a plane imaging type diffraction grating that diffracts incident light and condenses (images) the diffracted and dispersed light on a plane. A mechanism for linearly driving a unit consisting of an exit slit and a gas flow type proportional counter tube is provided along a plane dispersion (light collecting) plane formed by the diffraction grating, or a position-sensitive detector is provided.

(Ii) An aperture slit for adjusting the width and length of the undulator radiation incident on the sample is provided, and the width of the irradiation spot is formed to 1 mm or less. As a result, the fluorescent X-rays are separated with high resolution. Further, an orifice is provided before and after the aperture slit, and an undulator radiation light introducing device for differentially evacuating a chamber including the aperture slit is provided, thereby providing 10 ^-8 Torr.
The following undulator radiation light beam line that needs to be maintained in a high vacuum is connected to the X-ray fluorescence spectrometer.

(Iii) An X-ray fluorescence spectroscopy room including a gas flow type proportional counter using a polymer organic thin film as a window material and a measurement room are formed as separate structures, and an aperture having a role of an orifice is provided between the two rooms. And a differential evacuation pump is provided in the X-ray fluorescence spectroscopic chamber.

(Iv) In order to enable measurement of a gas sample, a gas introduction nozzle is provided just above the sample surface position in the measurement chamber through which the undulator radiation passes, and an exhaust duct is provided at a position facing the nozzle. An exhaust pump for directly differentially exhausting the measurement chamber is provided.

[0023]

In the X-ray fluorescence spectrometer of the present invention having the above-described structure, the width and length of the undulator radiation light are minutely formed by the aperture slit, and the undulator radiation light is applied to a minute portion of a solid or gas sample containing light element impurities. Irradiate. afterwards,
Fluorescent X-rays emitted from impurity atoms in the sample are made incident on a plane imaging type diffraction grating, and the fluorescent X-rays are focused on a planar dispersion surface. By moving the detector unit consisting of a gas flow type proportional counter and a slit along this plane dispersion plane, or by disposing a position sensitive detector such as a channel plate on this plane, the fluorescent X-ray Obtain a spectral spectrum. Further, in order not to hinder the ultra-high vacuum of 10 ^-8 Torr or less required by the undulator radiation light beam line, (i) the undulator light introduction chamber including the aperture slit and the orifice is differentially evacuated,
(Ii) An aperture serving as an orifice is provided between the measurement chamber and the X-ray fluorescence spectroscopy chamber to differentially evacuate the X-ray fluorescence spectroscopy chamber. (Iii) When a gas sample is used, a gas introduction nozzle The measurement chamber is evacuated directly from the exhaust duct provided just below the

[0024]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 are views showing the configuration of a fluorescent X-ray spectrometer according to the present invention. 1 is a top view in partial cross-section, and FIG. 2 is a side cross-sectional view as seen from the incident direction of undulator radiation.

The X-ray fluorescence spectrometer of the present invention mainly comprises a measurement room 1, an undulator radiation light introduction room 2, and an X-ray fluorescence room 3. In this apparatus, undulator radiation 4 from which radiant light energy can be arbitrarily selected is guided to the measurement chamber 1 through the undulator radiation light introduction chamber 2, and irradiates the solid sample 5 or the gas sample introduced from the gas introduction nozzle 6.

As is well known, the beam line of the undulator radiation 4 needs to be maintained in an ultra-high vacuum. Therefore, light passes through the orifices 8 provided before and after the aperture slit 7 and the undulator radiation light introduction chamber 2 is
Differential exhaust. Thereby, a one-digit pressure difference between the undulator radiation light introduction chamber 2 and the undulator radiation light beam line can be secured, and a three-digit pressure difference between the undulator radiation light introduction chamber 2 and the measurement chamber 1 can be secured.

When measuring a gas sample, a large-diameter exhaust duct 10 and an exhaust pump 11 are provided in the measurement chamber 1 at a position facing the gas introduction nozzle 6. The distal end of the gas introduction nozzle 6 and the distal end intake of the exhaust duct 10 are as close as possible to quickly exhaust the gas after passing the radiated light. The exhaust duct 10 and the exhaust pump 11 evacuate the measurement chamber 1 together with the exhaust pump 12 of the measurement chamber 1 so as to keep the inside of the measurement chamber 1 at a high vacuum.

In order to obtain a spectrum of the fluorescent X-rays 13 emitted from the solid sample 5 or the gas sample with high resolution,
The width and length of the incident undulator radiation 4 are formed to be 1 mm (width) × 10 mm (length) or less by the aperture slit 7. The fluorescent X-rays 13 emitted from the sample by the irradiation of the undulator radiation 4 are guided to a spectral plane imaging type diffraction grating 14 in the fluorescent X-ray spectroscopic chamber 3 shown in FIG.

An aluminum aperture 15 also serving as an orifice is provided between the measuring chamber 1 and the fluorescent X-ray spectroscopic chamber 3.
Is provided, and the fluorescent X-ray spectroscopy chamber 3 is differentially evacuated by the evacuation pump 16 to maintain a high degree of vacuum in the measurement chamber 1.

Fluorescent X-rays 1 separated by the diffraction grating 14
Numerals 7 are condensed on a planar dispersion surface 18 in the order of energy. In order to detect the separated fluorescent X-rays 17, a detection unit in which a gas flow type proportional counter 20 having a window 19 made of a polymer organic thin film and an emission slit 21 are integrated is used. The detection unit is configured to be movable along the dispersion surface 18.

By moving the detection unit along the dispersion surface 18 and detecting the separated fluorescent X-rays,
A fluorescent X-ray spectrum of a light element impurity contained in a sample can be obtained with high resolution.

By disposing a position-sensitive detector such as a channel plate along the dispersion surface 18 instead of the gas flow type proportional counter 20, it is possible to measure the fluorescent X-ray spectrum at a high speed with a high resolution. Will be possible.

Further, according to the present apparatus, if the detection range of the energy detector of the fluorescent X-ray is fixed and the intensity of the fluorescent X-ray detection value with respect to the energy of the incident undulator radiation light is measured, the impurity in the sample 5 can be obtained. It becomes possible to measure the structure near the X-ray absorption edge. FIG. 3 and FIG. 4 show B radiated from solid boron (B) sample 22 and solid boron nitride (BN) sample 23 realized by the present invention, respectively.
It is a spectrum measurement figure of -Kα fluorescent X-ray. FIG. 3 shows a spectrum obtained by fixing the energy of the incident undulator radiation light to about 210 eV, dispersing the energy of B-Kα fluorescent X-rays emitted from each sample irradiated with the radiation light, and detecting this. It is a measurement figure (B-K (alpha) ray spectrum). FIG. 4 shows that after fixing the measurement energy of the fluorescent X-ray detector so as to detect only the B-Kα ray, changing the energy of the incident undulator radiation, and dispersing the fluorescent X-ray emitted from the sample, FIG. 4 is a spectrum measurement diagram (emission spectrum near the B-Kα ray absorption edge) obtained by measuring with the detector.

The B-Kα fluorescent X-ray spectrum (FIG. 3)
From this, it is possible to analyze the electron orbital energy order between 2p-1s that changes depending on the bonding state of boron. Then, it becomes possible to analyze the chemical effect of the inner-shell excited state from the emission spectrum near the B-Kα ray absorption edge (FIG. 4).

[0036]

As described above, the present invention irradiates a sample with undulator radiation light, which is high-intensity light, and forms a planar imaging type light on a light irradiation path when the irradiation position on the sample is a light source point. By providing a diffraction grating, an optical system that does not require an incident slit, which has been conventionally required, is configured. Therefore, according to the present invention, fluorescent X-rays emitted from a sample can be efficiently detected.

Further, according to the present invention, by providing an aperture slit for adjusting the width and length of the undulator radiation light incident on the sample, and forming the irradiation spot width to 1 mm or less, the fluorescent X-ray can be converted to a high resolution. It becomes possible to split the light.

According to the present invention, an orifice is provided in the chamber for introducing undulator radiation light, differential exhaust is performed, and an aperture serving as an orifice is provided between the fluorescent X-ray spectroscopic chamber and the measuring chamber. By differentially evacuating the spectroscopic chamber, it is possible to secure a vacuum pressure difference between the undulator radiation light beam line and the measuring chamber of four digits or more, and therefore, it is necessary to maintain a high vacuum of 10 ^-8 Torr or less. A connection between an undulator radiation light beam line and an X-ray fluorescence spectrometer becomes possible. In this case, since the incident film of the polymer organic thin film of the proportional counter in the X-ray fluorescence spectroscopic chamber can be used as a single layer, it is possible to detect X-ray fluorescence with high efficiency.

Further, according to the present invention, a gas introduction nozzle is provided just above a sample surface position in the measurement chamber through which the undulator radiation passes, and an exhaust duct is provided at a position facing the nozzle to directly differentially exhaust the measurement chamber. A gas sample can be measured by providing an exhaust pump that performs the measurement. Therefore, by using the X-ray fluorescence spectroscopy method and apparatus of the present invention, since the fluorescence yield is as low as 1% or less, X-rays from light elements, which were difficult to detect with the conventional apparatus, can be obtained with high efficiency and high efficiency. It is possible to measure at a high resolution, and it is possible to analyze a light element impurity in a solid material and a chemical state of a gas-diluted sample containing a light element as a main component. In addition, in material production using a source gas containing a light element,
By simultaneously irradiating the sample with undulator radiation during the manufacturing process and observing the fluorescent X-rays emitted from the sample, application as a monitor of the material manufacturing process can be expected.

[Brief description of the drawings]

FIG. 1 is a top view showing the configuration of an X-ray fluorescence spectrometer according to the present invention.

FIG. 2 is a cross-sectional configuration view of the X-ray fluorescence spectrometer of the present invention as viewed from the incident direction of undulator radiation light.

FIG. 3 is a BKα ray spectrum measurement diagram emitted from a solid boron sample and a boron nitride sample realized by the apparatus of the present invention.

FIG. 4 is an emission spectrum measurement diagram in the vicinity of a B-Kα ray absorption edge emitted from a solid boron sample and a boron nitride sample realized by the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measurement room 2 Undulator radiation light introduction room 3 Fluorescence X-ray spectroscopy room 4 Undulator radiation light 5 Sample 6 Gas introduction nozzle 7 Aperture slit 8 Orifice 9 Exhaust pump 10 Exhaust duct 11 Exhaust pump 12 Exhaust pump 13 Fluorescent X emitted from sample Line 14 Planar imaging diffraction grating 15 Aperture 16 Exhaust pump 17 Spectroscopic X-ray fluorescence 18 Dispersion surface 19 Window of polymer organic thin film 20 Gas flow type proportional counter 21 Outlet slit 22 Spectrum from boron solid sample 23 Boron nitride Spectrum from solid sample

──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Shoji 14-8, Akaoji-machi, Takatsuki-shi, Osaka Prefecture Inside Rigaku Denki Kogyo Co., Ltd. (72) Akihiro Ikeshita 14-8, Akaoji-cho, Takatsuki-shi, Osaka Rigaku Denki Kogyo Co., Ltd. (56) References JP-A-63-186133 (JP, A) JP-A-1-242945 (JP, A) JP-A-60-111125 (JP, A) 149050 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 23/223 G21K 1/06 JICST file (JOIS)

Claims (10)

(57) [Claims] An undulator radiation light is used as an incident probe, and a plane imaging type diffraction grating is arranged on an irradiation path of light when an irradiation position of the undulator radiation light on a sample is used as a light source point. An X-ray fluorescence spectroscopy method, comprising detecting the separated X-ray fluorescence along a planar separation surface that converges the X-ray fluorescence. 2. A fluorescent X-ray separated by the diffraction grating is detected by linearly driving a detector unit including a gas flow type proportional counter and a slit along the planar separation surface. The X-ray fluorescence spectroscopy method according to claim 1, wherein: 3. The fluorescent X-ray according to claim 1, wherein the fluorescent X-ray separated by the diffraction grating is detected by a position-sensitive detector provided along the planar separation surface. Spectroscopic method. 4. The X-ray fluorescence spectroscopy method according to claim 1, wherein the width and the length of the light beam of the incident undulator radiation light are adjusted, and the undulator radiation light introduction path is exhausted. 5. An undulator radiation light introducing chamber for introducing undulator radiation light serving as an incident probe, a measurement chamber for installing a sample irradiated with the undulator radiation light, and an irradiation position of the undulator radiation light on the sample. And a fluorescent X-ray spectroscopy chamber provided with a planar imaging type diffraction grating provided on a light irradiation path in the case of a light source point, and emitted from the sample by irradiation of the undulator radiation light. An X-ray fluorescence spectrometer, wherein a detector unit is provided in the X-ray fluorescence spectroscopic chamber along a planar separation surface on which the X-rays to be emitted are separated and condensed by the diffraction grating. 6. The fluorescence X according to claim 5, wherein the detector unit comprises a gas flow type proportional counter and a slit, and is driven linearly along the planar separation surface. X-ray spectrometer. 7. An X-ray fluorescence spectrometer according to claim 5, wherein said detector unit comprises a position-sensitive detector. 8. The undulator radiation light introducing chamber is provided with a throttle slit, an orifice, and a differential pump for adjusting the width and length of the light flux of the incident undulator radiation light. Item X. Fluorescence X according to item 5.
X-ray spectrometer. 9. The X-ray fluorescence spectrometer is provided with a gas flow type proportional counter using a polymer organic thin film as an incident window material, and a differential pump. 3. The X-ray fluorescence spectrometer according to item 1. 10. The X-ray fluorescence spectrometer according to claim 5, wherein a gas introduction nozzle and an exhaust duct and an exhaust pump are attached to the measurement chamber at positions facing the nozzle.