JP3004388B2 - Reflection high-speed electron diffraction / soft X-ray emission spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection high-energy electron diffraction / soft X-ray emission spectrometer for analyzing the properties of a solid material, and more particularly, to the non-destructive electronic state and atomic arrangement state of a solid surface and an interface. The present invention relates to a reflection high-energy electron diffraction / soft X-ray emission spectrometer which has a great effect on analysis and the like.

[0002]

2. Description of the Related Art When electrons are incident on a substance and vacancies are generated in the inner electron levels of the constituent elements, X-rays are emitted with a certain probability. Soft X-ray emission spectroscopy is spectroscopy for spectrally separating X-rays in a wavelength region of about 1 to 50 nm among X-rays generated in this way. In the case of a solid substance, the electronic state of a valence band is determined. Suitable for examining. In particular, it has the feature that it is possible to clarify the electronic state of the valence band by dividing it into the symmetry of the wave function by the selection rule of transition involving light emission and absorption. Along with advances in detection technology and the like, it is being used for research on various solid substances.
These situations are described, for example, in “Vacuum” (Mitsuhiro Iwami et al.
3, No. 11, p. 848 (1990)).

[0003] Hereinafter, a conventional technique of the soft X-ray emission spectrometer will be described with reference to a schematic diagram of an example of the soft X-ray emission spectrometer shown in FIG.

In FIG. 2, reference numeral 21 denotes a vacuum chamber, and the pressure in the vacuum chamber 21 can be maintained at a level of 10 ⁻⁴ Pa by an exhaust system including an oil diffusion pump 22 and an oil rotary pump 23. . In the vacuum chamber 21, an electron gun 24, a sample stage 25, and a soft X-ray spectroscopic detector system 26 are installed. Soft X-ray installed in soft X-ray spectroscopic detector system 26
A gas flow / proportional coefficient tube is used for the line detector. The electron gun 24 is basically installed at a position facing the sample stage 25, and the electron beam emitted from the electron gun 24 basically enters the sample stage 25 perpendicularly. However, by tilting the sample stage 25, the incident angle of the electron beam can be changed in a range from vertical to horizontal. The soft X-ray spectroscopic detector system 26 is located above or obliquely above the surface of the sample stage 25. Further, the electron gun 24, the sample stage 25 and the soft X
The X-ray spectroscope 26 includes an electron gun controller 27 and a controller 2
8 and connected to a personal computer 29, the measurement and the subsequent data processing can all be controlled by the personal computer.

[0005] Si (Si) crystal having a (111) surface and Si— from titanium silicide (TiSi ₂ ) measured using a soft X-ray emission spectrometer shown in FIG.
The L _2,3 soft X-ray emission spectrum is shown in FIG. In a bulk material, these spectra show almost no change even if the incident electron beam energy (E _p ) is changed, and only the penetration depth of the electron beam changes. In other words, by changing the E _p, is that non-destructive depth profiling can. In FIG. 3, focusing on the spectrum near soft X-ray energy (wavelength): 90 eV, one peak is found around 92 eV in TiSi ₂ , but two peaks are found in the vicinity of 89 to 92 eV in the Si crystal. I understand. Further, the TiSi _2, (shown in figure E _F) the Fermi level prominent peak around is observed. This, s orbital electron state of Si in the TiSi ₂ is concluded to have a large density of states near E _F, This has become a approaching changes to previous thinking. Furthermore, the results of FIG. 3 also show the possibility of application to nondestructive analysis of a Si compound / Si junction system using a difference in the detected spectrum shape depending on the substance. As described above, soft X
A line emission spectrometer is a promising analyzer for nondestructive analysis of a property of a solid material, depth analysis, and the like.

[0006]

However, in the conventional soft X-ray emission spectrometer, a diffusion pump or the like using oil is used as a vacuum exhaust system, and the oil bag from the exhaust system to the vacuum chamber cannot be ignored. And the ultimate degree of vacuum in the vacuum chamber is at most 10 ⁻⁴ Pa,
Since the surface of the sample on the sample stage is covered with an adsorbed substance such as a residual gas in a vacuum chamber, a measurement sensitive to the surface cannot be performed. In addition, there is no means for providing information on the atomic arrangement on the sample surface. Therefore, there is a problem that the device configuration is not appropriate for investigating a phenomenon occurring on the very surface of the solid substance.

The present invention solves the above-mentioned problems of the prior art, and enables reflection high-speed electron diffraction and soft X-ray emission spectrometry in an ultra-high vacuum, and provides a clean solid surface, a solid surface on which foreign substances are adsorbed, It is another object of the present invention to provide a reflection high-speed electron diffraction / soft X-ray emission spectrometer capable of examining an electronic state and an atomic structure of an ultrathin film / substrate junction interface or the like in a short time.

[0008]

In order to achieve this object, the present invention provides an oil-free pump system capable of evacuating to an ultra-high vacuum as the evacuation means. Further, in addition to the configuration of the conventional device, it is provided with the diffraction electron beam detector system, electron gun, electron beam is disposed at a position obliquely incident with respect to the basic surface of the sample, at least, a soft against oblique incident electron beam X-ray
The soft X-ray is located at a position where it can enter the soft X-ray spectroscopic detector system.
Means such as disposing a spectral detector system were taken. Also, oblique
The reflected electron beam with respect to the incident electron beam is in the diffraction electron beam detector system
The diffracted electron beam detector system is placed at a position where
Measures were taken. As an additional factor, soft X-ray
Both the photodetector system and the diffracted electron beam detector system have the same data.
Connected to data import / processing system.

[0009]

According to the present invention, by taking the above measures, it is possible to eliminate the influence of adsorbed substances such as residual gas on the sample surface on the sample stage. In this state, only the intended foreign substance is adsorbed. In other words, it is possible to perform surface-sensitive measurement excluding the influence of adsorbed substances such as residual gas. In addition, since reflection high-speed electron diffraction measurement can be performed, information on the atomic structure of the surface and the like and the interface between the ultra thin film and the substrate can be obtained. Since the measurement by the electron beam is easy, the resolution in the depth direction is further improved, and it is possible and easy to obtain information on the electronic state such as the surface and the interface. Further, simultaneous measurement and analysis of reflection high-speed electron diffraction and soft X-ray emission spectroscopy can be performed on the surface / interface, and the electronic state and the atomic structure can be analyzed comprehensively in a short time.

[0010]

FIG. 1 is a schematic view of an embodiment of a reflection high-speed electron diffraction / soft X-ray emission spectrometer according to the present invention.

In FIG. 1, reference numeral 101 denotes a vacuum chamber of an all-metal seal, to which an exhaust system including a sputter ion pump 102 and a turbo molecular pump 103 is connected. With the above configuration, the vacuum chamber 101 can be maintained in an oil-free and clean ultra-high vacuum state under a pressure of 10 ⁻⁷ Pa or less. Evacuation of the vacuum chamber from the atmosphere (hereinafter,
A suction pump or the like may be used for "rough evacuation", and a titanium sublimation pump may be used for high-vacuum evacuation at the preceding stage after rough evacuation. Further, in the conventional apparatus, the soft X-ray spectroscopic detector system and the sample stage are installed in the same vacuum chamber, but in this embodiment, the soft X-ray spectroscopic detector system 104 and the sample stage 105 are further installed. The vacuum system 101 is made independent of the vacuum system, and both are connected by a differential evacuation system. Thereby, the ultra-high vacuum in the vacuum chamber 101 is further facilitated, and the cleaning of the sample surface on the sample stage 105 is improved.

A sample stage 105 is provided in a vacuum chamber 101.
Gun 106 and diffracted electron beam detector system 107
(A fluorescent screen is used in this embodiment), and the electron gun 106 is arranged at a position where the electron beam basically enters the sample surface on the sample stage 105 obliquely. The detector system 107 is arranged at a position where a reflected electron beam with respect to the incident electron beam can enter the detector system 107. In this embodiment, the oblique incident angle is several degrees or less (at least 10 degrees or less) so that the electronic state and the atomic state of the solid surface and the interface can be observed well. Further, the soft X-ray detector system 104 is also arranged at a position where the emitted soft X-ray detection direction makes a small angle with the sample surface. With the above configuration, reflection high-speed electron diffraction measurement can be performed, and soft X-ray emission spectrometry using obliquely incident electron beams can be simultaneously and effectively performed. On the other hand, the sample stage 10
By inclining 5, the incident angle of the electron beam can be changed in a range from vertical to horizontal, so that it is possible to cope with soft X-ray emission spectrometry similar to the conventional apparatus. The electron gun 106 changes the electron beam energy (E _p ) to several tens keV.
The diameter and current of the electron beam can be set to 1 μm or less and 2 μA or less, respectively. Due to the performance of the electron gun 106, local depth direction analysis can be performed. The soft X-ray spectroscopy detector system 104 arranged diagonally above and at a small angle to the sample stage 105 has a concave diffraction grating (gold coated on the surface, 600 to 1 mm).
2400 grooves) and an incident slit arranged on a Rowland circle, a Rowland circular mount type grazing incidence type diffraction grating spectroscopy system 108, and a position sensitive detector 109 combining a multi-channel plate and a photodiode array. With this configuration, high-resolution short-time measurement can be promoted also from the viewpoint of this configuration.

In addition to the above configuration, a sample stage 105,
The electron gun 106, the soft X-ray spectroscopic detector system 104, and the diffracted electron beam detector system 107 are connected to a personal computer 112 via an electron gun control device 110 and a control device 111. Automatic high-speed control.

[0014]

As described above, according to the present invention, by providing an oil-free pump system capable of ultra-high vacuum evacuation, it is possible to perform surface-sensitive measurement excluding the influence of adsorbed substances such as residual gas. A diffraction electron beam detector system is provided, and the electron gun is arranged at a position where the electron beam basically obliquely enters the sample surface, and at least a reflected electron beam for the obliquely incident electron beam is provided in the detector system. By arranging the detector system at a position where light can be incident, reflection high-speed electron diffraction measurement can be performed, and resolution in the depth direction can be enhanced in order to facilitate soft X-ray emission spectrometry with obliquely incident electron beams. The composition, atomic arrangement and chemical bonding state of the clean solid surface, the solid surface adsorbing foreign substances, and the ultra thin film / substrate junction interface, and the mechanism of the catalytic reaction Comprehensive any information, it is possible to provide a reflective can be measured and analyzed simultaneously and briefly high-energy electron diffraction, soft X-ray emission spectroscopy analyzer.

[Brief description of the drawings]

FIG. 1 shows reflection high-energy electron diffraction in one embodiment of the present invention.
Schematic diagram of soft X-ray emission spectrometer

FIG. 2 is a schematic diagram of a conventional soft X-ray emission spectrometer.

FIG. 3 shows a soft X-ray measured by a conventional soft X-ray emission spectrometer.
Of radiation spectrum

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 All-metal seal vacuum chamber 102 Sputter ion pump 104 Soft X-ray spectroscopy detector system 105 Sample stage 106 Electron gun 107 Diffraction electron beam detector system 1 using a fluorescent screen 1
07 109 Position sensitive detector

Continuation of the front page (72) Inventor Katsuhiko Muto 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd. (56) References JP-A-2-216040 (JP, A) JP-A Sho64 -86434 (JP, A) JP-A-56-84539 (JP, A) JP-A-4-24544 (JP, A) JP-A-57-148759 (JP, U) Motohiro Iwami et al., "Soft X-ray spectroscopy And Silicon Compounds and Thin Film Systems ”, Vacuum, 1990, Vol. 33, No. 11, P848-P853 (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 23/00-23/227 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A vacuum chamber provided with an oil-free pump system capable of evacuating to at least an ultra-high vacuum, a sample stage on which a sample is installed, an electron gun, a soft X-ray spectroscopic detector system, and diffraction electron beam detection. e Bei a vessel system, the vacuum chamber a sample stage soft X-ray detector system is installed
The vacuum system is installed independently of the vacuum system.
In addition, the electron gun applies an electron beam to the sample surface on the sample stage.
Arrange at a position where oblique incidence is possible.
Soft X-rays corresponding to the incident electron beam enter the soft X-ray spectroscopic detector system.
Place the soft X-ray spectroscopy detector system in a position where
And a reflection high-speed electron diffraction / soft X-ray emission spectrometer. 2. The soft X-ray spectroscopy detector system and the diffracted electron beam detector system are both connected to the same data acquisition / processing system or a plurality of mutually connected data acquisition / processing systems. and that claim 1 Symbol mounting, characterized in that the reflection high energy electron diffraction and soft X-ray emission spectroscopy analyzer. Claim 3. A which least obliquely incident electron beam reflection electron beam with respect to the a position that may be incident on the diffraction electron beam detector system, characterized by arranging the diffraction electron beam detector system
1 or the reflection high energy electron diffraction and soft X-ray emission spectroscopy analysis apparatus 2 according. 4. A soft X-ray detector system, serial to any one of claims 1 to 3, characterized in that it comprises a position sensitive detector that combines at least multi-channel plate and the photodiode array as a component < Reflection high-speed electron diffraction / soft X-ray emission spectrometer.