JPH1144665A - Auger electron spectroscopy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Auger electron spectroscopic analysis method, and particularly to a method for preparing a sample thereof.

[0002]

2. Description of the Related Art Auger electron spectroscopy is a method of irradiating a sample with an electron beam to excite inner core electrons of the sample, detecting emitted Auger electrons, and performing energy spectroscopy. FIG. 4 is a configuration diagram of a standard Auger electron spectrometer. An electron beam 9 obtained by finely narrowing electrons generated from the electron gun 1 by the lens system 2 is applied to a sample holder 11 in a sample chamber 13.
Irradiate the sample 5 placed on it and generate Auger electrons 1
0 is detected by the detector 3. The sample chamber 13 is evacuated by the exhaust device 8. The argon cylinder 6 on the left side of the figure is
Argon taken out through the pressure regulator 7 is supplied to the ion gun 4
This is for cases such as ionizing the sample 5 and irradiating the sample 5 to cut the surface of the sample 5.

In Auger electron spectroscopy, since the escape depth of Auger electrons is very small, a few nm, information on elements contained on the surface can be obtained as compared with other surface analysis methods.
In addition, it has features such as the ability to analyze the surface of a minute area by narrowing the electron beam. In recent years, a hot cathode field emission electron gun that can converge an electron beam extremely finely has been adopted, and an electron beam with a diameter of several tens of nanometers or less has been obtained. ing.

By the way, the electrons irradiated on the sample (hereinafter, referred to as
Although the incident electrons are hardly spread near the surface due to high energy, newly excited electrons due to back scattering inside the sample have a spatial distribution of several tens nm or more. FIG. 5A is an explanatory view showing electron scattering and Auger electron generation regions in Auger electron spectroscopy in the case of a flat sample. Usually, the center of scattering is several tens of
Although it is at a depth of nm, since the energy of Auger electrons is weak, electrons generated at a position deeper than a few nm from the surface cannot escape out of the sample, so that the influence on the analysis is small.

[0005]

However, the analysis site is
In the case of minute projections such as particles and projections having a diameter of several μm or less, incident electrons and secondary electrons may escape from the wall surface of the projection serving as the analysis unit and reach the substrate surface around the projection. FIG.
(B) is an explanatory diagram showing electron scattering and Auger electron generation regions in Auger electron spectroscopy in the case of a fine particle sample.

The electrons that have reached the surface of the substrate around the projection generate Auger electrons from the surrounding substrate, and the resulting spectrum includes not only information about the target projection but also information about the surface around the projection. Sometimes. For example, FIG. 6 shows a spectrum obtained by measuring an Auger spectrum of alumina (hereinafter, referred to as Al ₂ O ₃ ) particles having a diameter of 50 nm, 100 nm, and 1 μm on a silicon (hereinafter, referred to as Si) substrate.

FIG. 6 shows that the probe energy of incident electrons is 1
It is the result analyzed by Auger electron spectroscopy at 0 keV, probe current of 10 nA, and incident angle of 45 °. In the figure, D is the spectrum of a particle having a diameter of 50 nm, E is 100 nm, and F is 1 μm. In these spectra, silicon (Si) as a base is detected in all particles in addition to the elemental aluminum (Al) and oxygen (O) of the particles.

In the case described above, when it is clear that the information of the convex portion does not overlap with the information of the surrounding surface, it is possible to cope with the problem by separating the information. It was difficult to determine when there was a possibility that the same element was contained. As a countermeasure against the mixing of erroneous information from the surroundings, the spread of excited electrons depends on the energy of incident electrons.
A method of reducing the energy of the incident electrons is performed. Also,
There is also a method in which the angle of incidence of electrons is made nearly vertical to suppress excited electrons that escape from the side surface of the convex portion.

FIG. 7 shows that the probe energy of incident electrons is 3
It is a spectrum analyzed by Auger electron spectroscopy at keV, a probe current of 10 nA, and an incident angle of 45 °. In the figure, the spectrum of the particle is 50 nm in diameter, 100 nm in diameter, and 1 μm in diameter. From Al particles, only Al and O were detected, and Si was not detected.
From the particles of m, Si was detected in addition to Al and O.
Also, it can be seen that the peak intensity is lower than in FIG.

As described above, in the method of lowering the incident energy, the intensity of the peak of Auger electrons is reduced, it is difficult to distinguish the noise from noise, and the detection sensitivity is reduced. In addition, since the electron beam can be narrowed more when the incident energy is higher, there is a problem that when the incident energy is reduced, the irradiation range is widened and the analysis range is exceeded. FIG. 8 shows a spectrum analyzed by Auger electron spectroscopy at an incident angle of 90 ° with a probe energy of incident electrons of 10 keV and a probe current of 10 nA. In the figure, U is a spectrum of a particle having a diameter of 50 nm, S is 100 nm, and C is 1 μm. As in the case where the probe energy in FIG. 7 was lowered to 3 keV, only Al and O were detected from 1 μm particles and Si was not detected, but 50 nm and 100 nm were detected.
From the particles of nm, Si was detected in addition to Al and O. Also, it can be seen that the peak intensity is lower than in FIG.

As described above, in the method in which the incident angle is made closer to the vertical, the escape of Auger electrons together with the excited electrons is reduced, so that the detection sensitivity is lowered. In addition, it is difficult to completely suppress the escape of excited electrons, and there is a problem that it is difficult to make a distinction particularly when there is a possibility that the same element as the surrounding surface may be contained in a minute convex portion to be analyzed. Was. In view of the above problems, an object of the present invention is to provide an analysis method capable of performing accurate analysis by eliminating the influence of a portion other than the analysis target, particularly in the analysis of a minute convex portion.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an Auger electron spectroscopic analysis method for performing analysis by spectroscopy of Auger electrons generated during electron beam irradiation.
After coating the minute projections on the sample surface with a metal other than the one intended for analysis, the metal on the analysis site is removed, the analysis site is exposed, and the analysis is performed.

[0013] In this case, since the peripheral surface of the minute convex portion serving as the analysis site is coated with a known metal, Auger electrons from the peripheral surface generated by scattering of incident electrons and secondary electrons are not coated. It is only the known metal used in (1) and can be easily identified. Therefore, the desired composition of the minute projections can be easily and accurately obtained. In particular, if the surface of the sample is coated with a metal that does not exist in and around the analysis site of the sample, an accurate value can be obtained without mixing extra elements in the analysis result.

The metal coating the sample surface has a thickness of not less than 5 nm and a height of not more than the height of the minute convex portion which is an analysis site. As shown in the experimental results described below, if the thickness is less than 5 nm, the effect of the masking is insufficient, and the influence of the base may appear. On the other hand, if the height is higher than the height of the minute projections, which are the analysis sites, it becomes difficult to remove the metal coating.

As a metal for coating the surface of the sample, it is preferable to use a heavy metal. This is because light metals have a small masking effect and heavy metals have a large masking effect, as shown in the experimental results described later. As a method for removing the coating metal on the analysis site, it is preferable to use a focused ion beam apparatus.

The focused ion beam apparatus can narrow the ion beam finely and is suitable for processing a minute part.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments. Example 1 FIGS. 1A to 1C are explanatory views of a method for preparing a sample used in the analysis method of the present invention.

About 50 nm, 100 nm and 1 μm in diameter
The Si substrate 32 to which the Al ₂ O ₃ particles 31 were attached was used as a sample. [FIG. 1 (a)] A platinum (Pt) coating 33 having a thickness of about 10 nm is applied to the surface of the sample by an ion coater [FIG. 1 (b)]. As a coating method of Pt, any method can be used as long as Pt can be coated without damaging the sample surface, such as a vapor deposition method and application, and is not limited to an ion coater.

Next, using a focused ion beam apparatus, an ion beam 34 is formed on the Al ₂ O ₃ particles 31 on the substrate 32.
To expose the cut surface 31a [FIG. (C)]. The irradiation angle of the ion beam 34 was made shallow, and the upper part of the Al ₂ O ₃ particles 31 was shaved so as to be substantially parallel to the surface of the substrate 32 as shown in the figure. FIG. 2 is a configuration diagram of the focused ion beam device. Focused ion beam devices are largely
The apparatus comprises a sample chamber 24, an ion gun 23 and a secondary electron detector 14, and narrows down an ion beam 20 from the ion gun 23 to irradiate the sample 16 on a sample holder 22 for processing. The sample chamber 24 is evacuated by the exhaust device 19. As the ion beam 20, gallium ions generated by an ion gun 23 containing metal gallium were used. In this apparatus, secondary electrons generated when the ion beam 20 is irradiated are detected by the secondary electron detector 14, and the secondary electrons are observed on the monitor 15 as a tens of thousands times secondary electron image.
6 can be machined, and minute parts can be machined precisely.

The thus produced Al ₂ O ₃ particles 3
Auger electron spectroscopy was performed on the sample with the one cut surface 31a exposed. FIG. 3 is a spectrum spectrum analyzed by Auger electron spectroscopy at a probe energy of incident electrons of 10 keV, a probe current of 10 nA, and an incident angle of 45 °. In the figure, a is a spectrum of a particle having a diameter of 50 nm, b is 100 nm, and c is 1 μm.

In these spectra, Al, O, which is an element of the Al ₂ O ₃ particles 31, and Pt used for the Pt coating 33 are detected in all the particles, but Si of the substrate 32 is detected. Absent. That is, the analysis method of the present invention eliminates the influence other than the part to be analyzed,
It was confirmed that the analysis method was capable of accurate analysis. Example 2 A sample was prepared in the same manner as in Example 1 except that the thickness of the Pt coating on Al ₂ O ₃ particles was changed to 1, 3, 5, 30, 50, and 70 nm, and a probe for incident electrons was used. Analysis was performed by Auger electron spectroscopy at an energy of 10 keV, a probe current of 10 nA, and an incident angle of 45 °.

As a result, the thickness of the Pt coating was set to 1,
In the sample of 3 nm, Si, in addition to Al, O, and Pt,
Was detected. In other samples, Al, O, and Pt were detected.
And no Si was detected. Further, the thickness of Pt is set to 70
In the case of a sample with a diameter of 50 nm, particles with a diameter of 50 nm are exposed.
Al_TwoO_ThreeThe height of the particle 31 surface is Pt coated
Focused ion because it is lower than the height of the
It is difficult to work with the beam_TwoO _ThreeOn particles
May not be able to remove only the Pt coating
Was. For a sample with a Pt coating thickness of 50 nm
It did not matter.

From the above results, it is desirable that the thickness of the metal to be coated on the sample is 5 nm or more and not more than the height of the minute convex portion which is the analysis site. [Example 3] Pt was used as a metal to be coated on a sample.
, And gold and copper were used as representatives of heavy metals, and magnesium and strontium were used as representatives of light metals, and the same analysis as in Example 2 was performed. As a result, when the heavy metal was used, almost the same result as when Pt was used was obtained. In contrast, when a light metal was used, Si was detected at a coating thickness of 30 nm or less. When the coating is thickened, it is difficult to remove the coating of only the analysis portion at the minute projections as described in the second embodiment. Therefore, a heavy metal is preferable as the coating metal used for analyzing the minute projections.

[0024]

As described above, in the Auger electron spectroscopy method, after coating the minute projections on the surface of the sample with a metal other than the one intended for analysis, the surface of the sample is analyzed by a focused ion beam apparatus or the like. By removing the metal and exposing the analysis site, the analysis of the minute projections can be performed accurately and easily without being affected by the elements in the substances existing around as in the conventional case. It became so.

[Brief description of the drawings]

FIGS. 1A to 1C are explanatory views of a sample preparation method for an analysis method of the present invention.

FIG. 2 is a configuration diagram of a focused ion beam apparatus.

FIG. 3 shows an Auger electron spectroscopy spectrum according to the method of the present invention.

FIG. 4 is a configuration diagram of an Auger electron spectrometer.

5A is an explanatory diagram of electron scattering and an Auger generation region in Auger electron spectroscopy in the case of a flat sample, and FIG. 5B is an explanatory diagram of a fine particle sample.

FIG. 6 shows an Auger electron spectroscopy spectrum obtained by a conventional method.

FIG. 7 is an Auger electron spectroscopy spectrum at an acceleration voltage of 3 keV.

FIG. 8 shows an Auger electron spectroscopy spectrum at an incident angle of 90 °.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 electron gun 2 lens system 3 detector 4 ion gun 5 sample 6 argon cylinder 7 pressure regulator 8 exhaust device 9 electron beam 10 Auger electron 11 sample holder 12 ion beam 13 sample chamber 14 secondary electron detector 15 monitor 16 sample 19 Exhaust device 20 Ion beam 21 Secondary electron 22 Sample holder 23 Ion gun 24 Sample chamber 31 Al ₂ O ₃ particle 31a Cut surface of Al ₂ O ₃ particle 32 Si substrate 33 Pt coating 34 Ion beam

Claims (5)

[Claims] 1. An Auger electron spectroscopic analysis method for analyzing by spectroscopy of Auger electrons generated during electron beam irradiation,
An Auger electron spectroscopic analysis method, wherein a microprojection on the surface of a sample is coated with a metal other than that intended for analysis, and then the metal on the analysis site is removed to expose the analysis site. 2. The Auger electron spectroscopy method according to claim 1, wherein the surface of the sample is coated with a metal that does not exist in and around the analysis site of the sample. 3. The thickness for coating the sample surface is 5 nm.
The Auger electron spectroscopic analysis method according to claim 1 or 2, wherein the height is not more than the height of the minute convex portion as an analysis site. 4. As a metal for coating a sample surface,
4. The method for preparing an Auger electron spectrometry sample according to claim 1, wherein a heavy metal is used. 5. The Auger electron spectroscopic analysis method according to claim 1, wherein the coating metal on the analysis site is removed by a focused ion beam device.