JPH03188362A - Microstructure evaluating apparatus - Google Patents

Abstract

PURPOSE:To make it possible to analyze a structure highly accurately by using the electron beam from an electron gun having the high controllability of energy values together with high-resolution X rays from an X-ray source, and projecting the X rays and the electron beams on the same place of a sample at the same time. CONSTITUTION:An electron beams 7 is projected on a sample 1 in a vaccum state. The position on which the electron beam is projected is set at the same position on which X rays are applied. The energy of the electron beam 7 from the electron gun 5 is controlled. The X rays 2 are changed from the energy which is slightly lower than that at an absorbing end to the energy which is higher by about 1 keV and applied on the sample 1. The detection is performed with an X-ray detector 8 under the controlled state wherein the energy of the electron beam 7 and the energy of the X ray 2 are completely equal. When the X rays 2 having high resolution and the highly controllable electron beam 7 are applied on the same place in this way, sufficient measurement result is obtained even if the intensity of the X rays 2 is low.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a microstructure evaluation device for elucidating the atomic microstructure of a substance, particularly the structure of a thin film of 1 μm or less.

BACKGROUND ART Conventionally, as a method for analyzing the local structure of materials, extended X-ray absorption fine structure (Extended X-ray absorption
rption Fine 5structure1 or less,
(abbreviated as "EX AFS") has been proposed and is being implemented.

This method involves injecting monochromatic X-rays into a sample and continuously changing its wavelength to obtain the fine structure spectrum of the X-ray absorption that appears from the absorption edge of the target atom, such as the absorption edge on the high energy side. From the Fourier transform of the vibrational spectrum measured, the radial distribution around the specific atom of interest,
That is, it is a structural analysis method that determines the type, number, coordination, etc. of the nearest neighbor and second neighbor atoms. In other words, it is a fine oscillation of absorption that is observed continuously from the core absorption edge of the X-ray absorption spectrum to the high energy side of about 1 keV, and although it is a phenomenon that has been known for a long time, it can be analyzed using Fourier transform. After it was discovered that EXAFS can provide knowledge about short-range atomic arrangements around absorbing atoms, it suddenly came into practical use.

In structural analysis using EXAFS, synchrotron radiation (SOR) is often used as the X-ray source that enters the sample, but in recent years, EXAFS using a rotor target in the laboratory has been developed to make experiments easier. More and more measurements are being taken.

Problem to be Solved by the Invention However, in this case, the light intensity is 1/1000 to 10,000 of that of synchrotron radiation, so the fundamental problem is that it is difficult to achieve both X-ray intensity and resolution. occurs in In order to increase the X-ray intensity, for example, LiF (20
There is a method such as using a curved crystal such as 0),
In either case, the monochromaticity of X-rays (resolution) is inevitably reduced. Therefore, in a laboratory EXAFS apparatus using a rotor target, a method of continuous measurement for one week has been adopted, but the current situation is still not sufficient.

Means for Solving the Problems An X-ray source that generates X-rays, a monochromator that changes the energy of the X-rays irradiated onto a sample, a sample holder that holds the sample in vacuum, and a In addition to an X-ray detector that detects reflected X-rays, an electron gun was provided that was fixed to the sample holder and irradiated an electron beam onto the same area of the sample as the X-rays.

Effect: Using high-resolution X-rays and electron beams with extremely high controllability of energy values, by simultaneously irradiating the same part of the sample, an electron wave equivalent to the energy of the electron beam is emitted, which affects the X-rays. Therefore, even if the intensity of the X-rays is low, a high-resolution spectrum can be obtained in a short time, making it possible to perform highly accurate structural analysis.

Embodiment A first embodiment of the present invention will be explained based on FIG. In this example, X-rays 2 are transmitted through a sample 1 and changes in absorption of the X-rays 2 by substances are measured. First, X-ray 2
An X-ray source 3 is provided. This X-ray source 3
It is preferable to use a rotor target, which is mainly used in laboratories, but synchrotron radiation (SOR) may also be used.

Alternatively, a so-called plasma X-ray source or a laser X-ray source may be used, or an enclosed tube type may be used.

However, in terms of simplicity and ease of use, a rotor target that uses white X-rays generated by irradiating electron beams to targets such as W (tungsten), Mo (molybdenum), and Ag (silver) is sufficient.

X-rays 2 from this X-ray source 3 are incident on a monochromator 4, and the energy of the incident X-rays on the sample l to be measured is variably controlled. The monochromator 4 is not particularly limited. That is, in terms of good spectral characteristics, for example, a double monochrome crystal in which two channel-cut Si crystals are arranged symmetrically is preferable, but a single crystal plate or a curved monochrome crystal plate may also be used. This is because when the white X-rays generated by the X-ray source 3 are separated by the monochromator 4, the intensity decreases as the spectra are separated with better resolution.In this embodiment, the electron gun 5 This is because in the process up to this spectroscopy, attention is paid only to the resolution and not so much to the intensity.

Monochromatic X-rays 2 separated by a monochromator 4 are incident on a sample 1, which is held in vacuum (higher vacuum than 10'''' Torr) by a sample holder 6 in a bell jar (vacuum container). The sample size is from several μm to several tens of micrometers.
The thickness is about μm.

This is because if it is too thin, the amount of X-ray absorption will be insufficient, and if it is too thick, the amount of X-ray transmission will be insufficient, and this point is the same as in the case of conventional EXAFS. Further, the electron gun 5 is used to maintain the vacuum. This electron gun 5 is held and fixed to a sample holder 6, and emits an electron beam 7 to the sample 1 in vacuum.
irradiate it.

This irradiation position is set to be the same as the X-ray irradiation position.

Furthermore, the energy of the electron beam 7 emitted by the electron gun 5 is also controlled. For example, if the sample 1 is a copper foil, the energy of the electron beam 7 is controlled to be near the copper absorption edge of 8.898 keV. As in conventional EXAFS, the X-ray 2 is changed from an energy slightly lower than the absorption edge to an energy approximately 1 keV higher, and then enters the sample 1, so that the energy of the electron beam 7 and the energy of the X-ray 2 are exactly the same. It is detected by the X-ray detector 8 in such a controlled state.

In this way, by simultaneously irradiating the same location with the high-resolution X-rays 2 and the highly controllable electron beam 7, sufficient measurement results can be obtained even if the intensity of the X-rays 2 is low. . For example, in the case of the upper copper, the absorption edge of the copper is 8.
When an electron beam 7 with an energy slightly higher than 898 keV is incident, an electron wave is emitted from the copper atom, scattered from the surrounding copper atoms, and returned to the absorbing atom. The X-ray 2 (same energy) irradiated to the steel sample part in this state is absorbed, but it is affected by the above-mentioned electron waves, so if we obtain the spectrum of this X-ray 2, we can find that the copper Fine structures such as interatomic distance, coordination, and number are required. As the X-ray detector 8, commonly used scintillation counters, proportional counters, semiconductor device detectors (
Furthermore, a photostimulable phosphor (BaFBr; Er″t), which is called an imaging plate, may be used.

Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those shown in the previous embodiment are indicated using the same reference numerals. Basically, it is the same as the previous embodiment, but this embodiment has a film-like sample (
This is an example of an apparatus that irradiates X-rays 2 onto the surface of a sample 10 (1 μm or less) and measures the intensity of fluorescent X-rays generated from the sample 10. That is, this is applied when the substrate 9 does not allow the X-rays 2 to pass through.

The present embodiment is based on what is called (total internal reflection) fluorescence EXAFS as shown in, for example, Japanese Patent Application Laid-Open No. 62-214335, and the fluorescence X-rays are is generated, so that a fine structure (spectrum) can be obtained in the same way as EXAFS in the above embodiment. However, with mere conventional fluorescence EXAFS, the amount of fluorescent X-rays is so small that a sufficient spectrum cannot be obtained even if the measurement takes one week.

In this regard, in this embodiment, by making an essential improvement by simultaneously irradiating the same location with the electron beam 7 from the electron gun 5, it is possible to measure thin film samples that could not be measured with conventional laboratory fluorescence EXAFS equipment. That is.

In other words, it can be called electron beam assisted EXAFS, and while the photoelectron wave was generated by X-ray 2 with energy above the absorption edge, electron beam 7 is also added, and the X-ray absorption is reduced by the thin film. The thickness is sufficiently large and the spectrum becomes clear.

Also in this embodiment, the sample 10 (substrate 9) is held in vacuum by the sample holder 6. Then, the same location on the surface of the sample 10 is simultaneously irradiated with the X-ray 2 from the X-ray source 3 that has passed through the monochromator 4 and the electron beam 7 whose energy is controlled by the electron gun 5. At this time, the angle may be set at such a low angle that the surface of the sample 10 causes total reflection of the incident X-rays. The X-ray detector 8 of this embodiment may detect fluorescent X-rays from the surface of the sample 10, or in the case of total internal reflection, may directly detect the totally reflected X-rays. In any case, vibrations due to absorption of X-rays are obtained. In this case as well, as long as the X-rays 2 have a high resolution, their intensity does not necessarily have to be strong. This is because the electron beam 7 whose energy is precisely controlled is also irradiated from the electron gun 5, so if detection is performed with good resolution, sufficient data can be obtained in a short time (2 to 3 hours). It goes without saying that the energies of the electron beam 7 and the X-ray 2 are adjusted to be exactly the same, as in the previous embodiment.

In addition, in FIG. 2, the direction of the X-rays 2 separated by the monochromator 4 is changed because the monochromator 4
This is because a single crystal of 5i (Ill) was used, and it is due to its diffraction.

Effects of the Invention As mentioned above, the present invention uses high-resolution X-rays from an X-ray source and electron beams from an electron gun with extremely high controllability of energy values, and simultaneously irradiates the same part of the sample. Even in the case of low-energy X-rays such as those used in a laboratory, high-resolution spectra can be obtained in a short time, making it possible to perform highly accurate structural analysis.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, and FIG.
The figure is a schematic configuration diagram showing a second embodiment of the present invention.

Claims (1)

[Claims] an X-ray source that generates X-rays; a monochromator that changes the energy of the X-rays irradiated onto a sample; a sample holder that holds the sample in vacuum; A microstructure evaluation apparatus comprising: an electron gun that irradiates an electron beam to the same location as the specimen; and an X-ray detector that detects X-rays transmitted or reflected from the sample.