JP3198127B2 - X-ray spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, in the fields of surface analysis of semiconductor materials, particularly analysis of organic substances containing carbon, analysis of semiconductor manufacturing processes such as CVD, evaluation of organic electronic devices, and analysis of other biological materials, the number of fields has been increasing.蛍 光 X-ray fluorescence analysis using light in the soft X-ray region
SCA (Electron Spectroscopy for Chemical Analysy)
s: Esca), evaluation using methods such as Auger spectroscopy is required.

[0003] However, current commercially available evaluation devices use X as a light source.
Due to the use of the tube, only short-wavelength characteristic X-rays having a wavelength of several Å or less can be used. In the characteristic X-ray region having a short wavelength of several Å or less, the absorption coefficient of an organic substance mainly composed of carbon is small, the production rate of secondary electrons and Auger electrons is deteriorated, and the analysis sensitivity is deteriorated. In addition, since only X-rays of a specific wavelength can be used, diversified analysis cannot be performed.

In addition, research on artificial lattices for superconductivity of about several tens of degrees has been advanced, and there has been a strong demand for observing the internal structure of these artificial lattices in a non-destructive manner. However, in the conventional X-ray tube, only a wavelength of about several tens of millimeters can be used at the longest, so that the analysis by the X-ray diffraction method in the direct incidence region is impossible. For this purpose, the above-described analysis has been performed using an SOR light source that emits light up to the soft X-ray region in white. However, the SOR light source requires a large-scale facility, occupies a large space, is expensive, and is difficult for general users to use.

However, recently, a compact white X-ray light source has been developed, and the situation has changed, so that the general user can use the above-described analysis method easily. Specifically, such an X-ray light source has a pressure of 10 ^-4 To
When a target made of a material 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 not more than rr, the metal of the target enters a plasma state and has a wavelength of 5 ° or more. It emits white soft X-rays. Such an X-ray light source is called a laser plasma light source and emits high-intensity white X-rays. Therefore, a soft X-ray diffractometer and a photoelectron spectrometer already using the light source , X-ray acoustic spectroscopy and the like have been proposed.

As a representative soft X-ray diffraction analyzer using this laser plasma light source, the present applicant has filed Japanese Patent Application No. Hei.
No. 0897 filed. In this apparatus, X-rays generated by irradiating a metal target with an Nd: YAG laser beam are focused on an oblique incidence spectroscope through an incidence slit. Next, the X-rays separated by the grazing incidence spectrometer pass through the exit slit on the Rowland circle, are guided into a vacuum container for measurement, and are irradiated on the sample surface on the rotary table. X-rays scattered from the surface of the sample are measured by an X-ray detector such as an MCP or a channeltron. In the entire vacuum container for measurement, the emission slit for extracting X-rays can be moved to any position on the Rowland circle, so that monochromatic light can be used over a wide wavelength range.

[0007]

However, even in such an excellent measurement system, there is a problem that has not been solved yet. For example, short wavelength X shorter than 20 °
When spectrally measuring a line, it is necessary to move the vacuum container including the slit to a position where spectral separation can be performed at an extremely shallow oblique incidence angle by bringing the slit on the Rowland circle as close to the spectroscope as possible. In this case, long-wavelength light in the vacuum ultraviolet region of several hundred degrees or more is scattered on the surface of the spectroscope, and the required short-wavelength X-rays are not completely dispersed, and long-wavelength components are also mixed. Then, the light passes through the exit slit of the vacuum container for measurement together with the short wavelength component. This phenomenon is particularly noticeable in the short wavelength region where the intensity of the light source is weak because the exit slit approaches the spectroscope and becomes remarkable in the oblique incidence region where the scattering intensity is strong. For example, in the case of an X-ray diffractometer, it becomes impossible to measure diffraction efficiency.

The present invention has been made in view of the above-described problems, and it has been found that when spectroscopically measuring short-wavelength X-rays, scattered light from a spectroscope due to long-wavelength X-rays or vacuum ultraviolet light is reliably blocked. It is another object of the present invention to provide an X-ray spectrometer capable of separating high-purity short-wavelength X-rays.

[0009]

An X-ray spectrometer according to the present invention diffracts X-rays emitted from a laser plasma light source with a concave diffraction grating, and diffracts the diffracted light along the circumference of the Rowland circle of the concave diffraction grating. An X-ray spectrometer configured to irradiate an object through a slit movably provided and receive reflected, transmitted, or diffracted light from the object with an X-ray detector. A filter made of boron is provided in the optical path leading to the vessel so as to be insertable and removable. Further, in the X-ray spectrometer according to the present invention, the filter is arranged behind the concave diffraction grating.
It is characterized by being placed.

[0010]

Therefore, of the X-rays emitted from the laser plasma light source, the X-rays of the scattered light of the vacuum ultraviolet
Since the X-rays are blocked by a filter made of boron, only X-rays having a high purity of 20 ° or less and having a short wavelength can be transmitted through the filter to irradiate an object. Diffracted light is received by the X-ray detector.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a schematic configuration diagram of an X-ray spectroscopy apparatus. In the figure, reference numeral 1 denotes a vibration damping table that supports components while damping vibrations. Reference numeral 2 denotes a vacuum vessel installed on the vibration isolation table 1, which has a transparent window 3 made of glass and openings 4 and 5, and 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. Reference numeral 9 denotes a high-output pulse laser light source such as Nd: YAG, which is installed on the vibration isolation table 1, and reference numeral 10 denotes a condensing lens for condensing laser light, which collects laser light from the pulse laser light source 9. When the target 6 is irradiated by the lens 10 through the transparent window 3 and the shielding plate 8, a part of the target 6 is melted, evaporated and turned 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 the scattered contaminants from being deposited on the transparent window 3. In addition, the transparent window 3 and the shielding plate 8
Are 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 returns to the laser light source 9 and does not make 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 members constitute the soft X-ray light source unit 11.

Reference numeral 12 denotes another vacuum vessel which is installed on the vibration isolation table 1 and connected to the vacuum vessel 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 provided inside. The above members constitute the spectroscope 21.

Reference numeral 17 denotes a vacuum vessel at one end through an opening 13.
Telescopic bellows connected to 2, bellows 18
7, a vacuum vessel 18 connected to the other end of the bellows 17, for example, by being movable in both the longitudinal direction and the transverse direction of the bellows 17, so that the vacuum vessel 18 It is installed on the anti-vibration table 1 via a pedestal 19 that can move along. Reference numeral 20 denotes an exit slit which is installed in the vacuum vessel 18 at a position coinciding with the pedestal 19, that is, moves on 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 vessel 18, 23 is a first X-ray detector such as a channeltron installed rotatably about the sample table 22 in the vacuum vessel 18, The center of the diffraction grating 16, the center of the exit slit 20, and the center of the sample stage 22 are always located on a straight line. And the above-mentioned members comprise the measurement part 27.

Numeral 24 denotes a soft X which is set in the vacuum vessel 2 and
The second X for monitoring the intensity of the soft X-ray in the line light source unit 11
It is a line detector. 25 denotes a first X-ray detector 23 and a second X-ray detector
Is a computer that performs arithmetic processing based on an output signal from the X-ray detector 24 according to a predetermined formula, and 26 is a display device that displays the result of the arithmetic performed by the computer 25. The computer 25 controls the oscillation of the pulse laser light source 9, the rotation of the target 6, the movement of the pedestal 19, the rotation of the sample stage 22, and the rotation of the X-ray detector 23.

Reference numeral 28 denotes a magnetically levitated turbo-molecular pump having one end connected to the vacuum vessel 2 through the opening 5 and installed on the vibration isolator 1. 29 denotes a rubber tube 30 which hardly transmits vibration. , Which are connected to the other end of the turbo-molecular pump 28 via the oscillating pump and are provided outside the vibration isolator 1 for rough evacuation. These vacuum pumps perform evacuation in the vacuum vessel 2. 31.

Numeral 32 denotes a vacuum vessel at one end through the opening 14.
A magnetically levitated turbo molecular pump 33 connected to the vibration isolator 1 and 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 for evacuating the inside of the vacuum vessel 12, the bellows 17, and the vacuum vessel 18. The above configuration is the same as the configuration of the above-described prior art.

Next, reference numeral 36 denotes the spectroscope 16 and the exit slit 2.
The filter is disposed on the optical path between 0 and 0 to pass the short wavelength component of the dispersed X-ray, but to cut the long wavelength component which is the scattered light from the spectroscope 16. A filter (1200 mm thick) is used. still,
The arrangement position of the filter 36 is not limited to the position shown in FIG.
And any position on the optical path between them. Reference numeral 37 denotes a manipulator for operating the filter 36 from the atmosphere side outside the vacuum vessel so as to be inserted into and removed from the optical path. When a long wavelength component is used as measurement light, the filter 36 is used.
Can be moved out of the optical path.

Here, the filter 36 will be further described. As a material of the filter 36, substances having an atomic number of 17 or less and compounds containing these substances are particularly suitable.
FIG. 2 shows a partial example thereof. FIG. 2 shows Al, Al / C, A
1 shows the transmissivity in the X-ray region of a thin film composed of each substance of l / Ti, boron, indium, tin, and carbon. The wavelength (A) is plotted on the horizontal axis, and the transmissivity is plotted on the vertical axis. I have. In each graph of the figure, for example, “Al, 1500 °” in the upper left graph is an Al having a thickness of 1500 °.
This indicates that the film is a thin film, and “Al / C, 1500 ° Al, 270 ° C” in the graph on the right side is a thin film formed by joining Al having a thickness of 1500 ° and C having a thickness of 270 °. It is shown that. FIG. 3 shows FIG.
5 is an enlarged view of a main part of a graph showing the spectral transmittance of the Al thin film in FIG.

[0020] Then, as shown in FIGS. 2 and 3, the filter of each substance, whereas transmits the following short wavelength X-rays 40 Å, in the long wavelength region on 500Å or more as a rule of thumb is, X-ray transmittance is very low. Therefore, when performing a spectroscopic experiment in a short wavelength region of several tens of degrees or less, a filter 36 made of such a substance may be provided at any position on the optical path between the laser plasma light source and the X-ray detector 23. In this way, long-wavelength stray light due to scattering from the spectroscope 16 can be cut off, and X-rays of a short wavelength that is required can be extracted purely. Above all, B has no absorption edge in the short wavelength region, and thus can be said to be an excellent filter material.

Since the present embodiment is configured 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 a plasma. 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 vessel 2, enters the concave diffraction grating 16 through the entrance slit 15, and is separated.

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

Then, the soft X-ray a2 of the short wavelength component enters the sample S on the sample stage 22 through the exit slit 20, and the soft X-ray a3 diffracted by the sample S is detected by the X-ray detector 23. Is done. In this case, since only the soft X-ray a2 having a specific wavelength determined according to the positional relationship between the entrance slit 15, the diffraction grating 16 and the exit slit 20 is emitted from the exit slit 20, the movement of the base 19 causes the exit slit 20 to move. Move soft X-rays a2 passing through the exit slit 20.
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
By rotating, the incident angle of the soft X-ray a2 with respect to the sample S can be arbitrarily set. Further, the soft X-ray a3 from the sample S can be detected at an arbitrary diffraction angle by rotating the X-ray detector 23 around the sample stage 22.

When using long-wavelength X-rays, etc.,
Manipulator 3 from the atmosphere side outside the vacuum vessel
7 is operated to move the filter 36 out of the optical path. If the filter 36 is removed from the optical path, it can be used for measurement without attenuating X-rays when using long-wavelength X-rays. In the case of long-wavelength X-rays, the filter 36
, The exit slit 20 is sufficiently separated from the spectroscope 16 and has a large diffraction angle, so that the influence of scattered light is small.

According to the present embodiment as described above, by blocking the scattered light having a long wavelength from the spectroscope 16 by vacuum ultraviolet light by boron off <br/> filter 36, X-ray of high short wavelength purity Spectroscopy. Therefore, monochromaticity of X-rays in a short wavelength region is improved, and measurement accuracy is improved. In addition, since the filter 36 can be moved out of the optical path by the manipulator 37, the X-ray is not attenuated when long-wavelength X-rays are used. Also, by this filter 36,
It is possible to prevent scattered particles emitted from the laser plasma light source from entering the vacuum chamber 27 for measurement, which is also effective in preventing contamination and removing noise signals during measurement.

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

[0027]

X-ray apparatus according to the present invention as described above according to the present invention is, Fi of boron for transmitting X-rays and 20Å or less in a wavelength range to block the light in the vacuum ultraviolet wavelength region on the optical path and the material < The filter can be inserted and removed, so that long-wavelength X-rays and scattered light from the spectroscope due to vacuum ultraviolet light are cut off, and high-purity short-wavelength X-rays can be separated. Therefore, monochromaticity of X-rays in a short wavelength region is improved, and measurement accuracy can be improved. Further, this filter can prevent scattered particles emitted from the laser plasma light source from entering the vacuum vessel for measurement, which is effective for preventing contamination and removing noise signals during measurement.

[Brief description of the drawings]

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

FIG. 2 is a graph showing the transmittance of each substance constituting 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. 2;

[Explanation of symbols]

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

Continuation of front page (56) References JP-A-1-295146 (JP, A) JP-A-63-27741 (JP, A) JP-A-62-223657 (JP, A) JP-A-62-38350 (JP, A) , A) JP-A-57-44842 (JP, A) JP-A-61-176443 (JP, U) JP-A-47-12954 (JP, Y1) Tanaka Nakao, “Laser plasma X-ray source and its application”, Optical Technology Contact, (1989), Vol. 27, No. 4, P187-P193 (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 23/00-23/227 G21K 3/00 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. An X-ray emitted from a laser plasma light source is diffracted by a concave diffraction grating, and the diffracted light is passed through a slit provided to be movable along the circumference of a Rowland circle of the concave diffraction grating. irradiating the reflection from said object, the transmitted or diffracted light in the X-ray apparatus that is received by the X-ray detector, in the optical path from the previous SL plasma light source in the X-ray detector, and the material of boron An X-ray spectrometer characterized by being provided with a filter that can be inserted and removed . 2. The method according to claim 1, wherein the filter is located behind the concave diffraction grating.
2. The X-ray spectroscopy according to claim 1, wherein the X-ray spectroscopy is arranged at
apparatus.