JPH0599863A - X-ray spectroscope - Google Patents

Abstract

PURPOSE:To interrupt the scattered light of long wave length from a spectroscope used for vacuum ultraviolet light and make possible the spectral diffraction of highly pure short wave length in an X-ray. CONSTITUTION:A detachably mounted filter 36 is provided on a light path between a laser plasma light source 9 and an X-ray detector 23. The filter 36 is composed of a substance of 17 or less in atomic number or its compound, for instance, a boron filter, the X-ray of 20Angstrom or less of a short wave length area is transmitted therethrough and scattered light from a spectroscope 16 used for the X-ray of long wave length and vacuum ultraviolet light is interrupted. In the case where the X-ray of the long wave length is used, the filter 36 is moved out of a light pass by the use of a manipulator 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray spectroscopic apparatus for irradiating a sample with spectroscopic X-rays and measuring reflected light or diffracted light from the sample to examine the properties of the sample.

[0002]

2. Description of the Related Art Recently, in the fields of surface analysis of semiconductor materials, especially analysis of organic substances containing carbon, analysis of semiconductor manufacturing processes such as CVD, evaluation of organic electronic devices, analysis of other biological substances, etc. X-ray fluorescence analysis using light in the soft X-ray region above Å as a probe, E
SCA (Electron Spectroscopy for Chemical Analysy
s: Esca), Auger (auger) spectroscopy, etc. are required for evaluation.

However, current commercial evaluation devices use X as the light source.
Since a ray tube is used, only characteristic X-rays with a short wavelength of a few Å or less can be used. In the characteristic X-ray region of a short wavelength of a few Å or less, the absorption coefficient of the organic substance mainly composed of carbon is small, the production rate of secondary electrons and Auger electrons becomes poor, and the analytical sensitivity is poor. In addition to this, since only X-rays of a specific wavelength can be used, multilateral analysis cannot be performed.

In addition, researches on artificial lattices for superconductivity of about several tens of liters are also progressing, and there is an increasing demand for nondestructive observation of the internal structure of these artificial lattices. However, in the conventional X-ray tube, only the wavelength of several Å can be used at the longest, so that the analysis by the X-ray diffraction method in the direct incidence region was impossible. Therefore, the above-mentioned analysis was performed using a SOR light source that emits white light up to the soft X-ray region. However, since the SOR light source requires a large-scale facility, it occupies a large space and is expensive, making it difficult for general users to use it.

However, the situation has recently changed due to the development of a compact white X-ray light source, and it has become possible for general users to familiarize themselves with the above-mentioned analysis methods. To specifically describe such an X-ray light source, the atmospheric pressure is 10 ⁻⁴ To
When a target made of a substance such as a metal is irradiated with a laser beam having an intensity of 10 ¹² W / cm ² or more in a vacuum of rr or less, the metal of the target becomes a plasma state and white light having a wavelength of 5 Å or more is obtained. That is, the soft X-rays of this type emit light. The X-ray light source of this type is called a laser plasma light source and is an X-ray light source that emits white X-rays with high brightness. Therefore, a soft X-ray diffractometer and a photoelectron spectrometer using this light source have already been used. , X-ray acoustic spectroscopy, etc. have been proposed.

As a typical soft X-ray diffraction analyzer using this laser plasma light source, the present applicant has filed Japanese Patent Application No. 2-25.
Some of them have been filed with No. 0897. In this apparatus, X-rays generated by irradiating a metal target with Nd: YAG laser light are focused on an oblique incidence spectroscope through an entrance slit. Next, the X-rays dispersed by the oblique incidence spectroscope pass through the injection slit on the Rowland circle, are guided into the vacuum container for measurement, and are irradiated on the sample surface on the rotary table. The X-ray scattered from the sample surface is measured by an X-ray detector such as MCP or channeltron. Since the X-ray extraction emission slit can be moved to any position on the Rowland circle in the entire measurement vacuum container, monochromatic light can be used over a wide wavelength range.

[0007]

By the way, even in such an excellent measurement system, there are still unsolved problems. For example, a short wavelength X shorter than 20Å
In the case of spectrally measuring a line, it is necessary to bring the slit on the Rowland circle as close as possible to the spectroscope and move the vacuum container including the slit to a position where the slit can be split at a very shallow oblique incident angle. In that case, long-wavelength light in the vacuum ultraviolet region of several hundred liters or less scatters on the surface of the spectroscope, and the originally required short-wavelength X-rays are not completely dispersed, and long-wavelength components are also mixed. Then, it passes through the injection slit of the measuring vacuum container together with the short wavelength component. This phenomenon is particularly remarkable in the oblique incidence region where the emission slit is close to the spectroscope and the scattering intensity is strong, and thus is seriously affected in the short wavelength region where the intensity of the light source is weak. For example, in the case of an X-ray diffractometer, the measurement becomes impossible when measuring the diffraction efficiency.

In view of the above problems, the present invention reliably blocks scattered light from a spectroscope due to long-wavelength X-rays and vacuum ultraviolet light when measuring by spectrally measuring short-wavelength X-rays. It is an object of the present invention to provide an X-ray spectroscope capable of spectroscopically analyzing short-wavelength X-rays.

[0009]

An X-ray spectroscopic device according to the present invention diffracts X-rays emitted from a laser plasma light source by a concave diffraction grating, and diffracts this diffracted light along the circumference of a Rowland circle of the concave diffraction grating. In an X-ray spectroscopic device in which an object is irradiated through a slit provided so as to be movable, and reflected, transmitted, or diffracted light from the object is received by an X-ray detector, X-ray detection from a laser plasma light source A filter that blocks light in the vacuum ultraviolet wavelength range and transmits X-rays of 20 Å or less is provided in the optical path to the container.

[0010]

Therefore, among X-rays emitted from the laser plasma light source, X-rays in the long wavelength region such as scattered light in the vacuum ultraviolet wavelength region
Since the rays are blocked by the filter, only high-purity short-wavelength X-rays of 20 Å or less can pass through this filter and illuminate the object, and the reflected, transmitted, or diffracted light from the object is X-rays. The light is received by the detector.

[0011]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 shows a schematic configuration diagram of an X-ray spectroscopic apparatus. In the figure, reference numeral 1 denotes an anti-vibration table that supports structural members while damaging vibration. Reference numeral 2 denotes a vacuum container installed on the vibration isolation table 1, which has a transparent window 3 made of glass and openings 4 and 5, and has a target 6 made of a metal material such as gold inside the shaft 7. A transparent shielding plate 8 made of glass and having substantially the same size as the window 3 is provided inside the transparent window 3 so as to be rotatable. Reference numeral 9 denotes a high-power pulse laser light source such as Nd: YAG, which is mainly installed on the vibration isolation table 1, and 10 denotes a condenser lens for condensing the laser light, which condenses the laser light from the pulse laser light source 9. When the target 6 is irradiated with the lens 10 through the transparent window 3 and the shielding plate 8, a part of the target 6 is melted and evaporated into plasma, and soft X-rays are generated from the high temperature and high density plasma. ing. These function as a laser plasma light source.

At this time, the shielding plate 8 prevents scattered pollutants from being deposited on the transparent window 3. The transparent window 3 and the shielding plate 8
Is installed at an angle of about 3 ° with respect to the optical axes of the laser light source 9 and the condenser lens 10 so that the reflected light of the laser light by them does not return to the laser light source 9 and makes the oscillation of the laser light unstable. An antireflection film is provided so that the target 6 can be efficiently irradiated with laser light. The above-mentioned members form the soft X-ray light source unit 11.

Reference numeral 12 denotes another vacuum container installed on the vibration isolation table 1 and connected to the vacuum container 2 through the opening 4,
In addition to having openings 13 and 14, an entrance slit 15 and a concave diffraction grating (oblique incidence type diffraction grating) 16 are installed inside. The above-described members constitute the spectroscope 21.

One end of the vacuum container 1 has an opening 13 through the opening 13.
Telescopic bellows connected to 2, 18 is bellows 1
7 is another vacuum container connected to the other end of 7, and the vacuum container 18 can be moved in both the longitudinal direction and the lateral direction of the bellows 17 so that the vacuum container 18 can move in the circumference of the Rowland circle of the diffraction grating 16. It is installed on the vibration isolation table 1 via a pedestal 19 that is movable along the vibration isolation table 1. Reference numeral 20 denotes an injection slit installed in the vacuum container 18 at a position corresponding to the pedestal 19, that is, moving along the Rowland circle of the diffraction grating 16 with the movement of the pedestal 19. 22
Is a sample table rotatably installed in the vacuum container 18, 23 is a first X-ray detector such as a channel tron installed rotatably around the sample table 22 in the vacuum container 18, The center of the diffraction grating 16, the exit slit 20, and the center of the sample table 22 are always positioned on a straight line. The above-mentioned members constitute the measuring unit 27.

Reference numeral 24 denotes a soft X which is installed in the vacuum container 2.
Second X for monitoring the intensity of soft X-rays at the line light source unit 11
It is a line detector. 25 is the first X-ray detector 23 and the second
A computer for performing arithmetic processing according to a predetermined formula based on an output signal from the X-ray detector 24, and a display device 26 for displaying the arithmetic result by the computer 25. The computer 25 also controls oscillation of the pulse laser light source 9, rotation of the target 6, movement of the pedestal 19, rotation of the sample table 22, and rotation of the X-ray detector 23.

28 is a magnetic levitation type turbo molecular pump, one end of which is connected to the vacuum container 2 through the opening 5 and which is installed on the vibration isolation table 1, and which has little vibration. 29 is a rubber tube 30 which hardly transmits vibration. Is a rotary pump for rough evacuation, which is connected to the other end of the turbo molecular pump 28 via the and which is installed outside the vibration isolation table 1, and is a vacuum pump part for performing evacuation in the vacuum container 2. 31 is configured.

One end of the vacuum container 32 has an opening 14 through the opening 14.
2 is a magnetic levitation type turbo molecular pump installed on the vibration isolation table 1; 33 is connected to the other end of the turbo molecular pump 32 via a rubber tube 34;
A rotary pump for roughing installed outside,
These constitute a vacuum pump unit 35 that evacuates the vacuum container 12, the bellows 17, and the vacuum container 18. The above configuration is the same as the configuration of the above-mentioned prior art.

Next, 36 is the spectroscope 16 and the emission slit 2.
It is a filter that is arranged on the optical path between 0 and 0 and that passes the short wavelength component of the separated X-ray but cuts the long wavelength component that is the scattered light from the spectroscope 16. In the present embodiment, it is a boron. A filter (thickness 1200Å) is used. still,
The arrangement position of the filter 36 is not limited to the position shown in FIG. 1, but the laser plasma light source and the X-ray detector 23
It may be at any position on the optical path between and. Reference numeral 37 is a manipulator for operating the filter 36 from the atmosphere side outside the vacuum container to insert / remove it into / from the optical path.
Can be moved out of the optical path.

Here, the filter 36 will be further described. As the material of the filter 36, substances having an atomic number of 17 or less and compounds containing these substances are particularly suitable.
Some examples are shown in FIG. Fig. 2 shows Al, Al / C, A
The transmittances in the X-ray region of the thin films composed of 1 / Ti, boron, indium, tin, and carbon are shown respectively, and the horizontal axis shows the wavelength (A) and the vertical axis shows the transmittance. There is. In each graph of the figure, for example, "Al, 1500Å" in the upper left graph is Al with a thickness of 1500Å
This is a thin film, and "Al / C, 1500Å Al, 270Å C" in the graph on the right side of the graph is a thin film formed by joining Al with a thickness of 1500 Å and C with a thickness of 270 Å. It is shown that. Also, FIG. 3 is shown in FIG.
3 is an enlarged view of a main part of a graph showing the spectral transmittance of the Al thin film in FIG.

As shown in FIG. 2 and FIG. 3, the filter of each substance transmits X-rays having a short wavelength of 40 Å or less, whereas, as a rough guideline, the X-rays in the long wavelength region of 500 Å or less are used. Line transmittance is very low. Therefore, when a spectroscopic experiment is performed in the short wavelength region of several tens of liters or less, if a filter 36 made of such a substance is arranged at any position on the optical path between the laser plasma light source and the X-ray detector 23. By blocking stray light of long wavelength due to scattering from the spectroscope 16, purely required short wavelength X-rays can be extracted. Above all, Be, B, Al, C and compounds containing these substances are preferable. Especially, since elements such as Be and B having a small atomic number have no absorption edge in the short wavelength region,
It can be said that it is an excellent filter material.

Since the present embodiment is constructed as described above, when the pulse laser light source 9 is oscillated to irradiate the target 6 with laser light, a part of the target 6 is melted and evaporated to form plasma, and this plasma is used. Soft X-ray a1 is generated. The generated soft X-ray a1 is guided to the entrance slit 15 through the opening 4 of the vacuum container 2, enters the concave diffraction grating 16 through the entrance slit 15, and is dispersed.

The soft X-ray a2 separated by the diffraction grating 16 is
Although it passes through the boron filter 36, only the short wavelength component passes through it at this time, and the long wavelength component which is the scattered light from the spectroscope 16 is cut. This boron filter 36 is
As shown in FIG. 2, the short wavelength component of 20 Å or less has a transmittance of 80%, while the long wavelength component of 500 Å or more has a transmittance of 1% or less, which is ideal. It can be said that it is a filter.

The short-wavelength soft X-ray a2 enters the sample S on the sample table 22 through the emission slit 20, and the soft X-ray a3 diffracted by the sample S is detected by the X-ray detector 23. To be done. In this case, since only the soft X-ray a2 having a specific wavelength determined according to the positional relationship among the entrance slit 15, the diffraction grating 16 and the exit slit 20 is emitted from the exit slit 20, the pedestal 19 moves to cause the exit slit 20 to move. Is moved, the soft X-ray a2 passing through the injection slit 20 is moved.
The wavelength is changed, that is, wavelength scanning is performed. Therefore, since the wavelength of the soft X-ray a2 incident on the sample S changes, the spectral reflectance and the like of the sample S can be measured. Also, the sample table 22
The incident angle of the soft X-ray a2 with respect to the sample S can be arbitrarily set by rotating. Further, by rotating the X-ray detector 23 around the sample table 22, the soft X-ray a3 from the sample S can be detected at an arbitrary diffraction angle.

When using long-wavelength X-rays, etc.,
Manipulator 3 from the atmosphere side, which is the outside of the vacuum container, etc.
7 is operated to move the filter 36 out of the optical path. When the filter 36 is removed from the optical path, it is possible to use the long wavelength X-rays for measurement without attenuating the X-rays. In the case of long wavelength X-rays, the filter 36
Even if the light is not passed through, the exit slit 20 is sufficiently separated from the spectroscope 16 and the diffraction angle is large, so that the influence of scattered light is small.

As described above, according to this embodiment, the filter 36 blocks the scattered light of the long wavelength from the spectroscope 16 due to the vacuum ultraviolet light, and enables the high-purity short-wavelength X-ray spectroscopy. .. Therefore, the monochromaticity of X-rays in the short wavelength region is improved, and the measurement accuracy is improved. Moreover, since the filter 36 can be moved to the outside of the optical path by the manipulator 37, the X-ray is not attenuated when the long-wavelength X-ray is used. Further, the filter 36 can prevent scattered particles emitted from the laser plasma light source from entering the measurement vacuum container 27, and is effective in preventing contamination and removing a noise signal during measurement.

When the filter 36 and the target 6 are made of the same substance, the spectral characteristics do not change even if the scattered particles emitted from the laser plasma light source adhere to the filter 36, which leads to an improvement in the measurement accuracy. Can be said.

[0027]

As described above, since the X-ray spectroscopic device according to the present invention is provided with a filter for blocking light in the vacuum ultraviolet wavelength range and transmitting X-rays in the wavelength range of 20 Å or less on the optical path, By blocking scattered light from the spectroscope due to long-wavelength X-rays and vacuum ultraviolet light, it becomes possible to disperse highly pure short-wavelength X-rays, which improves monochromaticity of X-rays in the short-wavelength region. The measurement accuracy can be improved. In addition, this filter can prevent scattered particles emitted from the laser plasma light source from entering the measurement vacuum container, and is also effective in preventing contamination and removing noise signals during measurement.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an X-ray spectroscopic device according to the present invention.

FIG. 2 is a graph showing the transmittance of each substance forming a filter.

FIG. 3 is an enlarged view of a main part of a graph showing the transmittance of Al in the graph of FIG.

[Explanation of symbols]

 6 Target 16 Concave Diffraction Grating 20 Emission Slit 23 X-ray Detector 36 Filter

[Procedure amendment]

[Submission date] January 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

However, the situation has recently changed due to the development of a compact white X-ray light source, and it has become possible for general users to familiarize themselves with the above-mentioned analysis methods. To specifically describe such an X-ray light source, the atmospheric pressure is 10 ⁻⁴ To
When a target made of a substance such as a metal is irradiated with a laser beam having an intensity of 10 ¹² W / cm ² or more in a high vacuum of rr or less, the metal of the target becomes a plasma state and a wavelength of 5 Å or more is emitted. It emits white soft X-rays. The X-ray light source of this type is called a laser plasma light source and is an X-ray light source that emits white X-rays with high brightness. Therefore, a soft X-ray diffractometer and a photoelectron spectrometer using this light source have already been used. , X-ray acoustic spectroscopy, etc. have been proposed.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

By the way, even in such an excellent measurement system, there are still unsolved problems. For example, a short wavelength X shorter than 20Å
In the case of spectrally measuring a line, it is necessary to bring the slit on the Rowland circle as close as possible to the spectroscope and move the vacuum container including the slit to a position where the slit can be split at a very shallow oblique incident angle. In that case, long wavelength light in the vacuum ultraviolet region of several hundred liters or more scatters on the surface of the spectroscope, and the originally required short wavelength X-rays are not completely dispersed, and long wavelength components are also mixed. Then, it passes through the injection slit of the measuring vacuum container together with the short wavelength component. This phenomenon is particularly remarkable in the oblique incidence region where the emission slit is close to the spectroscope and the scattering intensity is strong, and thus is seriously affected in the short wavelength region where the intensity of the light source is weak. For example, in the case of an X-ray diffractometer, the measurement becomes impossible when measuring the diffraction efficiency.

Claims (1)

[Claims] 1. An X-ray radiated from a laser plasma light source is diffracted by a concave diffraction grating, and the diffracted light is passed through a slit provided so as to be movable along the circumference of a Rowland circle of the concave diffraction grating. In the X-ray spectroscopic device in which the X-ray detector receives the reflected, transmitted or diffracted light from the object, a vacuum ultraviolet wavelength range is provided in the optical path from the laser plasma light source to the X-ray detector. An X-ray spectroscopic device comprising a filter that shields the above light and transmits X-rays of 20 Å or less.