JP3151709B2 - Elemental analysis method and elemental analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elemental analysis method for irradiating an analysis sample with a particle beam and performing elemental analysis of the analysis sample using characteristic X-rays emitted from the analysis sample. Further, the present invention relates to an elemental analyzer for achieving the elemental analysis method.

[0002]

2. Description of the Related Art Conventionally, an elemental analyzer of this type has a structure shown in FIG.
Electron beam microanalyzer (EPMA: E)
Electron Probe Micro Analysis
zer) has been widely used. This electron beam microanalyzer uses an electron beam as a particle beam, irradiates the electron beam to an analysis sample, and strikes out electrons of atoms in the analysis sample by electrons incident on the analysis sample, thereby forming an electron beam in the analysis sample. The characteristic X-ray is emitted from the analysis sample by setting the atom to an excited state, and the characteristic X-ray emitted from the analysis sample is detected to specify the element of the analysis sample.

More specifically, this electron beam micro analyzer has an electron beam generator 10 for generating an electron beam. The irradiation mechanism including the lens 12 and the scanning coil 13 irradiates the analysis sample 11 with the electron beam, and strikes the electrons incident on the analysis sample 11 to the electrons of the atoms in the analysis sample 11 to thereby analyze the analysis sample. Is set to an excited state to emit characteristic X-rays from the analysis sample 11. The X-ray detector 14 detects characteristic X-rays. This X
The detection result of the line detector 14 is used for elemental analysis of the analysis sample 11. The analysis sample 11 is placed on the sample fine movement device 15, and the position of the analysis sample 11 in the vacuum chamber 16 is finely adjusted by the sample fine movement device 15. The vacuum chamber 16 is maintained at a predetermined degree of vacuum by a vacuum pump 17.

[0004]

However, in the above-mentioned electron beam microanalyzer (EPMA), the X-ray generation region (that is, the elemental analysis region) has a depth of several μm.
m], the elemental analysis of the outermost surface layer of the substance is impossible (see FIG. 3).

More specifically, an acceleration voltage: V ₀ [k
V], the average atomic weight: A, the average atomic number:
Z, the X-ray generation region (that is, the elemental analysis region) when incident on a substance having an average density: ρ [g / cm ³ ] has a critical excitation voltage: V _k [kV] (where V ₀ > V _k , V ₀ Is smaller than V _k, no characteristic X-ray is generated), and a depth of 0.033 (V ₀ ^1.7 −V _k ^1.7 ) A / ρZ [μm]
(Usually several [μm]). According to this equation, for example, an X-ray generation region (ie, an elemental analysis region) when an electron beam of 10 [kV] is injected into silicon.
Is about 1.3 [μm] deep.

As described above, in an electron beam microanalyzer (EPMA) using electrons as incident particles,
Excitation voltage: V _k [kV] to generate characteristic X-rays
There is a problem that electrons having high energy (usually several [kV]) or more must be injected, and only element analysis in a deep region such as a depth of several [μm] can be performed.

An electron beam microanalyzer (EPM)
A) Auger electron spectroscopy (AES: Auger Electron Speech) as an elemental analysis method in a shallower region than A)
However, even with this method, the elemental analysis region is only up to several nm in depth, and elemental analysis of the outermost surface layer of the substance was impossible (see FIG. 3).

Further, as a conventional method for elemental analysis of the outermost surface layer of a substance, secondary ion mass spectrometry (SIMS: Seconda) has been proposed.
ry Ion Mass Spectroscoopy)
However, this method is a destructive analysis in principle, and there is a problem that a sample cannot be analyzed in a nondestructive manner (see FIG. 3).

It is therefore an object of the present invention to provide an element analysis method capable of performing non-destructive element analysis of the outermost surface layer of a substance of an analysis sample.

Another object of the present invention is to provide an elemental analyzer capable of performing nondestructive elemental analysis of the outermost surface layer of a substance of an analysis sample.

[0011]

According to the present invention, there is provided an element analysis method for irradiating a particle beam to an analysis sample and performing elemental analysis of the analysis sample using characteristic X-rays emitted from the analysis sample. The positron beam is used as the particle beam, the incident energy of the positron beam to the analysis sample is controlled in the range of 1 V to 100 kV, and the positron beam is irradiated on the analysis sample, and the material of the analysis sample is analyzed. An elemental analysis method characterized by performing elemental analysis at a depth ranging from the surface layer to about several μm is obtained.

Further, according to the present invention, a positron beam generator for generating a positron beam, irradiation means for irradiating the analysis sample with the positron beam and emitting characteristic X-rays from the analysis sample, X-ray detector for detecting, the incident energy of the positron beam to the analysis sample is irradiated with the positron beam in the range of 1 V to 100 kV to the analysis sample, from the material outermost layer of the analysis sample An elemental analysis apparatus characterized by performing elemental analysis at a depth in a range up to about several μm is obtained.

Further, according to the present invention, the positron beam generator can change an incident energy of the positron beam to the analysis sample in a range of 1 V to 100 kV, and can analyze an elemental analysis region of the analysis sample by the analysis. An elemental analyzer characterized by being variable in the range from the outermost surface layer of the sample to about several μm is obtained.

[0014]

As described above, in the present invention, a positron beam is used as a particle beam, and the positron beam is irradiated on the analysis sample, and the positrons incident on the analysis sample are annihilated with the electrons of the atoms in the analysis sample. By causing the atom in the analysis sample to be in an excited state to generate a characteristic X-ray,
Electron beam micro analyzer (EPMA), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS)
Nondestructive elemental analysis of the outermost surface layer of a substance, which was not possible with such methods, has become possible.

"Characteristic X-rays" are emitted when a substance is normally irradiated with an electron beam or the like to strike out the inner shell electrons of the atoms, change the atoms to an excited state, and return to the original base state from that state. , A line spectrum-like X-ray unique to each element.
In "characteristic X-ray generation by positrons", instead of hitting a substance with a positron beam instead of an electron beam and "striking out the inner core electrons of an atom", "annihilating the inner core electrons of an atom with an incident positron" As a result, the atoms are changed to an excited state, and characteristic X-rays are generated. This method enables non-destructive elemental analysis of the outermost surface layer of the substance, elemental analysis with small background noise, elemental analysis of a substance that was impossible with an electron beam, and the like.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, an elemental analysis apparatus for achieving the elemental analysis method according to one embodiment of the present invention includes the same parts indicated by the same reference numerals as those in FIG. This elemental analyzer has a positron beam generator 20 for generating a positron beam as a particle beam. Hereinafter, a positron beam microanalyzer (PPMA: Positron) will be described.
Probe Micro Analyzer). In the positron beam microanalyzer (PPMA), an irradiation mechanism including a lens 12 and a scanning coil 13 irradiates the positron beam to the analysis sample 11, and converts the positrons incident on the analysis sample 11 into atoms of the analysis sample 11. The characteristic X-rays are emitted from the analysis sample 11 by extinguishing the electrons with the electrons to make the corresponding atoms in the analysis sample 11 into an excited state. The X-ray detector 14 detects the characteristic X-ray. The detection result of this X-ray detector 14 is
Used for elemental analysis of

The positron beam generator 20 has a positron beam incident energy on the analysis sample 11 of 1 V to 100 k.
A positron beam in the range of V is generated.

The electron detector 21 detects secondary electrons or reflected electrons emitted from the analysis sample 11 when the positron beam is incident on the analysis sample 11, and obtains a microscope image of the surface of the analysis sample 11.

A gamma ray detector (not shown) for detecting an annihilation gamma ray generated when a positron incident on the analysis sample 11 is annihilated with an electron in the analysis sample 11 is provided, and X-ray detection and simultaneous counting are performed. May be taken.

A positron detector (not shown) for detecting a positron scattered by the analysis sample 11 due to the positron beam incident on the analysis sample 11 may be provided to obtain a positron image.

Further, the electron beam generator 1 shown in FIG.
0 may be used together. In this case, when the electron beam generator 10 is started up instead of the positron beam generator 20, the irradiation mechanism including the lens 12 and the scanning coil 13 irradiates the analysis sample 11 with the electron beam, and impinges on the analysis sample 11. By hitting the electrons of the atoms in the analysis sample 11 with the generated electrons, the atoms in the analysis sample 11 are excited to emit characteristic X-rays from the analysis sample 11. Further, the X-ray detector 14 detects the characteristic X-ray, and the detection result of the X-ray detector 14 is used for elemental analysis of the analysis sample 11.

Next, the positron beam microanalyzer (P
(PMA) will be described.

As the positron beam, a beam obtained by using an accelerator such as a cyclotron or an electron linear accelerator, or a β ⁺ decaying isotope is used. Positrons are accelerated to a predetermined energy and then converted into a lens (convergent lens or objective lens)
The aperture is squeezed at 12 and irradiated onto the analysis sample 11. An astigmatism correction coil (not shown) may be used to make the positron beam formed on the analysis sample 11 a perfect circle.

Scanning coil (positron beam deflection coil) 1
Reference numeral 3 denotes a coil for arbitrarily scanning an incident positron beam on the surface of the analysis sample 11, and by scanning a cathode ray tube (not shown) in synchronization with the coil 13, displays any signal change on the cathode ray tube. can do.

The sample fine movement device 15 is provided with X,
It performs Y (horizontal direction), Z (vertical direction) movement, rotation, inclination, and the like.

The X-ray detector 14 normally uses a wavelength-dispersive X-ray spectrometer (WDS), but may include an energy-dispersive X-ray spectrometer (EDS). The former feature lies in its excellent wavelength resolution, and the latter feature is that multi-element simultaneous analysis is possible.

The electron detector 21 comprises, for example, a scintillator and a photomultiplier tube, and detects secondary electrons and reflected electrons. Further, reflected electrons can be detected by a semiconductor detector.

As the vacuum pump 17, a rotary pump, a diffusion pump, a turbo molecular pump, an ion pump or the like is used.

An observation optical system (not shown) is used together with the sample fine movement device 15 to search and confirm the analysis position of the analysis sample 11 and to focus the analysis position on the X-ray spectroscope. I do.

If necessary, detection and analysis of positrons are performed using the above-described positron detector (not shown), and annihilation γ-rays are generated using the above-mentioned γ-ray detector (not shown). It is also effective to perform detection / analysis of the data.

Furthermore, a magnetic field generated by a positron beam guiding coil (not shown) may be used to guide the positron beam.

Here, the merits of using positrons instead of electrons as incident particles will be described in comparison with an electron beam micro analyzer (EPMA).

As described above, in the case of an electron beam microanalyzer (EPMA) using electrons, an excitation voltage: V _k [kV] (usually several [k
V]), an electron having a higher energy than that must be injected, and only elemental analysis in a deep region such as a depth of about several μm was possible. For this reason, elemental analysis of the outermost surface layer of a substance was impossible with an electron beam microanalyzer (EPMA) using electrons.

On the other hand, in a positron microanalyzer (PPMA) using positrons as incident particles,
The excitation voltage: V _k becomes 0 due to the energy balance when the positron annihilates with the electron in the analysis sample. That is,
X-rays can be generated from any low-energy positron, and by using such low-energy (several to several tens of volts) positrons, elemental analysis of the outermost surface layer of a material is possible without destruction. (See FIG. 3).

More specifically, the acceleration voltage: V ₀ [k
V] of the positron beam, average atomic weight: A, average atomic number:
Z, an X-ray generation region (that is, an elemental analysis region) when incident on a substance having an average density of ρ [g / cm ³ ] has a depth of 0.
033 V ₀ ^1.7 A / ρZ [μm] (sub [angstrom] to several [μm]), which is the lower limit of acceleration voltage: V ₀ (that is, excitation voltage: V _k ) that was present when using an electron beam. Disappears (becomes 0). Therefore, it is possible to generate X-rays even with a positron having sufficiently low energy (several to several + [V]), and such a positron having sufficiently low energy (several to several tens [V]) is incident on the sample. If this is the case, elemental analysis of the outermost layer of the substance becomes possible in a non-destructive manner. Also, by gradually increasing the energy of the positron, nondestructive elemental analysis in the depth direction from the outermost surface layer of the substance to the vicinity of the substance surface and further deeper becomes possible.

As described above, an electron beam microanalyzer (EPMA) can only perform elemental analysis in a deep region up to a depth of about several μm, whereas a positron beam microanalyzer (PPMA) can From the outermost surface layer to the vicinity of the surface of the material and further deeper, nondestructive elemental analysis in the depth direction from the outermost surface layer of the material to several [μm] in depth becomes possible. In particular, electron beam microanalyzers (EPM
The greatest feature is that elemental analysis of the outermost surface layer of the material, which was not possible with A), can be performed nondestructively with a positron beam microanalyzer (PPMA).

When a positron having sufficiently low energy (several to several tens of volts) is incident, the background noise generated at that time is considerably small, and the accuracy (S
/ N) can be obtained as a feature of the positron beam microanalyzer (PPMA).

Further, an annihilation gamma ray emitted when the incident positron annihilates with an electron in the analysis sample is detected, and coincidence with X-ray detection is performed, so that the accuracy by further background noise removal is improved. (S / N) may be improved.

As described above, the use of the positron makes it possible to perform the analysis with higher accuracy (S / N) than the case where the electron is used. This means that the use of positrons enables analysis with a smaller amount of charge than the use of electrons, that is, the effect of irradiating the sample is small. Therefore, analysis of the surface of an insulating material sample that is sensitive to charging and analysis of adatoms loosely bonded to the surface, which were impossible with an electron beam microanalyzer (EPMA), have been performed by a positron beam microanalyzer (PPM).
What is possible in A) is a great feature.

Next, the positron beam microanalyzer (P
PMA) will be described.

1) A positron beam obtained by using an accelerator such as a cyclotron or an electron linear accelerator or a β ⁺ decaying isotope is accelerated to a predetermined energy, and the lens 1
The light converges at 2 and enters the analysis sample 11. At this time, the energy of the positron beam is variable from 1 [V] to 100 [kV], and accordingly, the elemental analysis region is also variable from the outermost surface layer of the substance to about several [μm]. In particular, when the energy of the positron beam is sufficiently low (several to several tens [V]),
Non-destructive elemental analysis of the outermost surface layer of the substance becomes possible. The positron beam may be guided by a magnetic field generated by the positron guiding coil (not shown).

2) The incident positron beam is scanned on the surface of the analysis sample 11 using the scanning coil 13. The electrons generated at this time are detected by the electron detector 21 and a morphological observation of the surface of the analysis sample 11 can be performed by obtaining a microscope image.

3) The sample fine movement device 15 adjusts and confirms the analysis position using the above-mentioned microscope image and the above-mentioned observation optical system (not shown).

4) The characteristic X-ray emitted from the sample 11 is X
The light is detected by the line detector 14 and element analysis is performed. Further, a more detailed analysis may be performed by using the above-described positron detector (not shown) or the above-mentioned γ-ray detector (not shown) in combination.

The main principle of the present invention, "characteristic X-ray generation by positron", can be widely applied to other cases where characteristic X-rays are emitted from a substance and used. That is, (1) “analytical positron microscope” using “characteristic X-ray generation by positron”, (2) “soft X-ray appearance voltage spectrum method” using “characteristic X-ray generation by positron”, (3) “ "X-ray generator" using "characteristic X-ray generation by positron", (4)
The main principle of the present invention is a new apparatus such as an "X-ray diffraction apparatus" using "characteristic X-ray generation by positron" and (5) an "X-ray fluorescence analyzer" using "characteristic X-ray generation by positron". Can be devised by applying.

[0047]

As described above, according to the present invention,
A positron beam is used as a particle beam, the positron beam is irradiated to the analysis sample, and the positrons incident on the analysis sample are annihilated with the electrons of the atoms in the analysis sample, thereby setting the atoms in the analysis sample to an excited state. By generating characteristic X-rays by electron beam microanalyzer (EP
MA), Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), and the like, enabling nondestructive elemental analysis of the outermost surface layer of a substance. In addition, by changing the energy of the incident positron beam, the non-destructive element in the depth direction from the material outermost layer to a depth of about several μm from the material outermost layer to the vicinity of the material surface and further deeper. Analysis becomes possible. Furthermore, if the beam diameter of the incident positron beam is sufficiently reduced, three-dimensional non-destructive elemental analysis in which the plane direction is added in the depth direction is also possible.

In the present invention, since positrons having sufficiently low energy (several to several tens of volts) can be used, the background noise generated can be reduced, and data with high accuracy (S / N) can be obtained. Obtainable. Further, if the annihilation γ-ray emitted when the incident positron annihilates with the electron in the analysis sample is detected and the coincidence counting is performed with the X-ray detection, the analysis can be performed with higher accuracy.

Further, as described above, in the present invention, the analysis can be performed with higher accuracy than the electron beam microanalyzer (EPMA).
The analysis can be performed with a smaller charge amount, and the irradiation effect on the analysis sample can be reduced. As a result, the present invention enables analysis of the surface of an insulating material sample that is sensitive to charging and analysis of adsorbed atoms loosely bonded to the surface, which were not possible with an electron beam microanalyzer (EPMA).

[Brief description of the drawings]

FIG. 1 is a schematic view of an elemental analyzer for achieving an elemental analysis method according to one embodiment of the present invention.

FIG. 2 is a schematic diagram of an elemental analysis device that achieves a conventional elemental analysis method.

FIG. 3 is a diagram for explaining an element analysis method of the related art and the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Electron beam generator 11 Analytical sample 13 Scanning coil 14 X-ray detector 15 Sample fine movement device 16 Vacuum chamber 17 Vacuum pump 20 Positron beam generator 21 Electron detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-93644 (JP, A) JP-A-6-347555 (JP, A) Patent 2917092 (JP, B2) Patent 2590417 (JP, B2) VISHNEVSKY I . N. , Et. al. , "EXCATION OF NUCLEI Rh, Ag, AND Au INDUCED BY THE POSITRON ANNIHILATION ON THE BOUND ELECTRONS OF AN ATOM", Yad Fiz, 1983. 38, No. 2, pp. 273-279 (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 23/22-23/227 JICST file (JOIS) WPI (DIALOG)

Claims (3)

(57) [Claims] 1. An elemental analysis method for irradiating an analysis sample with a particle beam and performing an elemental analysis of the analysis sample using characteristic X-rays emitted from the analysis sample, wherein a positron beam is used as the particle beam. Then, the incident energy of the positron beam to the analysis sample is controlled in the range of 1 V to 100 kV to irradiate the analysis sample with the positron beam, and several μm from the material outermost layer of the analysis sample.
An elemental analysis method comprising performing elemental analysis at a depth in a range up to about m. 2. A positron beam generator for generating a positron beam, irradiation means for irradiating an analysis sample with the positron beam and emitting characteristic X-rays from the analysis sample, and X-ray detection for detecting the characteristic X-ray And irradiating the analysis sample with the positron beam whose incident energy of the positron beam to the analysis sample is in the range of 1 V to 100 kV, and adjusting the positron beam to about several μm from the material outermost surface layer of the analysis sample. An element analyzer for performing elemental analysis at a depth within a range. 3. The elemental analyzer according to claim 2, wherein the positron beam generator varies an incident energy of the positron beam to the analysis sample in a range from 1 V to 100 kV. An elemental analysis apparatus characterized in that an elemental analysis area is variable in a range from the outermost surface layer of the analysis sample to about several μm.