JPH07151711A - Method and device for surface analysis - Google Patents

Abstract

PURPOSE:To provide a method capable of analyzing specimen surface for every atomic layer and a device realizing the method. CONSTITUTION:In a low energy ion scattering spectroscope(LEISS), using a device provided with a vacuum chamber 1 capable of providing a superhigh vacuum better than 1X10<-9> Torr, an ion gan 2 capable of irradiating rare gas ions of two or more kinds to a secimen 4, and a detector 3 of ion scattered by the specimen 4, He ion is irradiated to the specimen for analysis under the superhigh vacuum better than 1X10<-9>Torr, Ne ion is irradiated to the specimen 4 to analyze the surface and exactly remove one atomic layer and He ion is again irradiated to the surface newly exposed to analyze. By repeating this process, the analysis goes in depth.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a surface analysis method and apparatus. More specifically, it is possible to evaluate the types of elements constituting the sample surface and their bonding states, and to analyze the distribution in the depth direction by removing the sample surface for each atomic layer, especially for several atomic layers on the surface. The present invention relates to a method and an apparatus for implementing the method.

[0002]

2. Description of the Related Art An accelerated ion beam is incident on a sample,
Measure the energy distribution of the scattered and returning ions,
The method of analyzing a sample is called ion scattering spectroscopy. Among ion scattering spectroscopy, slow ion scattering spectroscopy using low energy ions of about keV (hereinafter referred to as LEISS)
And Rutherford backscattering spectroscopy (hereinafter referred to as RBS) using high-energy ions of about MeV.

Both LEISS and RBS are used for elemental analysis and bonding state / crystallinity analysis of thin films, and especially LEI.
In the case of SS, it is effective for analyzing the bond state and crystallinity of one atomic layer on the sample surface. On the other hand, with RBS, elemental analysis and crystallinity evaluation from the sample surface to the inside are possible, but only the average value of a considerably thick portion can be obtained. Therefore, conventionally, when performing a detailed analysis of the inside of the sample, the sample surface is etched by sputtering using Ar ions or reactive ion etching, and the analysis is repeated by a surface analysis method such as the LEISS method. I was evaluating.

[0004]

However, when the inside of the sample is analyzed by the above-mentioned conventional method, there are the following problems. First, when etching the sample surface,
It is extremely difficult to control the etched thickness with the accuracy of the atomic layer unit. Therefore, it is almost impossible to analyze the detailed distribution of elements having a thickness of several atomic layers from the sample surface. Further, the sample surface exposed by etching is in an active state with a high potential, and is easily bonded to the residual gas in the device, so that it is easily contaminated.
Therefore, the influence of contaminants in the analysis after surface treatment cannot be ignored. Further, due to etching, the atomic arrangement may be destroyed, or the gas component used for etching or the etched substance may remain on the surface. These also reduce the accuracy of analysis.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art by elemental analysis in the depth direction for each atomic layer from the surface without disturbing the atomic arrangement of the sample or causing contamination. An object of the present invention is to provide a surface analysis method and apparatus capable of analyzing binding states and the like.

[0006]

According to the present invention, a method of injecting a low energy ion beam into a sample, measuring the energy distribution of scattered ions, and analyzing the sample is described. A process of injecting small rare gas ions into the sample and analyzing the sample surface, and a process of injecting large mass rare gas ions into the sample and removing the sample surface by sputter etching for each atomic layer thickness. And a step of again injecting a rare gas ion having a small mass into the sample to analyze the sample surface, the surface analysis method is provided.

In the method of the present invention, it is preferable that two or more kinds of rare gas ion beams having different masses are incident on a sample to perform analysis with different resolutions. For example, a beam of a large mass rare gas ion is used as a sample. It is preferable to measure the energy distribution of the rare gas ions scattered on the sample surface when the sample is incident and sputter-etch the sample surface, and analyze the sample surface. Further, in the method of the present invention, it is preferable that the diameter of the rare gas ion beam is made small, for example, focused to about 1 mm for analysis. Further, it is preferable to perform the analysis while scanning the rare gas ion beam relative to the sample, and it is further preferable to perform the analysis while changing the incident angle of the rare gas ion beam.

In the method of the present invention, each step of injecting rare gas ions into the sample is preferably carried out under an ultrahigh vacuum of 1 × 10 ^-9 Torr or more, and each rare gas ion has an energy of 1 keV or less. It is preferable to perform analysis and sputter etching by injecting into the sample.

On the other hand, according to the present invention, a vacuum chamber capable of evacuating the interior to a high vacuum, and an ion beam provided in the vacuum chamber and accelerated to a predetermined energy of two or more kinds of rare gas ions having different masses are used for the vacuum. Provided is a surface analysis device comprising: an ion source configured to be incident on a sample in a chamber at a predetermined angle; and a measuring unit for measuring an energy distribution of ions scattered by the sample. To be done. It is preferable that the apparatus of the present invention further comprises means for focusing the ion beam to a predetermined diameter, and the measuring means is configured to be capable of measuring the energy distribution of the ions scattered in the predetermined angular range.

[0010]

According to the method of the present invention, a beam of a rare gas ion having a small mass is incident on a sample at a low energy and the surface is analyzed by the ions scattered, and a beam of a rare gas ion having a large mass is also accelerated at a low energy. The main feature is that the single atomic layer on the surface is removed by being incident on the sample, and the newly exposed sample surface is analyzed again using a low energy beam of a rare gas ion having a small mass. According to the method of the present invention, it is possible to perform elemental analysis and bond state analysis in the depth direction for each atomic layer from the surface of the sample.

In the method of the present invention, in order to perform highly accurate analysis, it is preferable that two or more kinds of rare gas ion beams having different masses are incident on the sample to perform analysis with different resolutions. In this case, it is also preferable to simultaneously perform analysis with rare gas ions having a large mass during the above-described sputter etching. In the method of the present invention, as the rare gas ions having a small mass, for example, He ions are preferable, and the ion beam energy is preferably 1 keV or less. The mass of the rare gas ions and the energy of the ion beam are selected so that the elemental analysis and the bond state analysis of one atomic layer only on the sample surface can be performed without damaging the sample as much as possible. When the He ion beam is incident on the sample with energy of 1 keV or less, elemental analysis and bond state analysis of the surface can be performed with almost no damage to the sample surface.

On the other hand, in the method of the present invention, it is preferable to use, for example, Ne as the rare gas ion having a large mass,
The energy of the ion beam is still preferably 1 keV or less. When the Ne ion beam is incident on the sample at an energy of 1 keV or less, only one atomic layer on the sample surface is affected, and thus the sputter-etched region also stays within this range. The mass of the rare gas ions and the energy of the ion beam may be selected so that the sample surface can be precisely etched, that is, one atomic layer can be stripped from the sample surface. Therefore, it is possible to use Ar ions having a large mass by limiting the acceleration energy.

Further, in the method of the present invention, the steps of the above analysis and sputter etching are performed at 1 × 10 ^-9 Torr.
It is preferable to carry out under the above ultra-high vacuum. this is,
In each process, if the irradiation and detection of the ion beam is performed under ultra-high vacuum, it is possible to suppress the scattering due to the residual gas, and especially to prevent the contamination of the surface of the sample having a high potential newly exposed by the sputter etching. Because you can. Further, in the method of the present invention, it is preferable that the diameter of the rare gas ion beam is narrowly focused to, for example, about 1 mm during the analysis, and the range of about 5 × 5 mm ² on the sample surface is scanned with the rare gas ion beam. It is preferable. Furthermore, the incident angle of the rare gas ion beam is, for example, ± 20.
It is preferable to perform the analysis while changing the degree. This enables accurate analysis without missing extremely small areas (two-dimensionally and three-dimensionally) on the sample surface, and the surface area newly exposed by sputter etching is very small. However, it can be analyzed.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following disclosure is merely examples of the present invention and does not limit the technical scope of the present invention.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic view of a surface analysis apparatus of the present invention which realizes the method of the present invention. The apparatus shown in FIG. 1 is equipped with an exhaust port 10 and is capable of evacuating to an ultrahigh vacuum up to a pressure of 1 × 10 ⁻⁹ Torr or less, an ion gun 2 mounted on the side surface of the vacuum chamber 1, and a detection chamber. A vessel 3 is provided. Further, a manipulator 6 is provided on the upper part of the vacuum chamber 1, and a sample holder 5 having a heater 7 for heating is attached on the manipulator 6. The manipulator 6 can move the substrate in three directions x, y, and z (that is, two directions parallel to the paper surface of the drawing and a direction perpendicular to the paper surface), and the substrate can be moved in two axes (the axes of the manipulator 6). It can be tilted about a parallel axis and an axis perpendicular to the paper surface. The ion gun 2 has two or more rare gas introduction holes 20 for introducing two or more kinds of rare gases, and emits a rare gas ion generated by ionizing the rare gas inside into a beam. The ion gun 2 is provided with an electro-optical means 21 such as a lens and a deflection electrode.
The position and angle of are also adjustable. With the ion gun 2 and the manipulator 6 having such a configuration, it is possible to focus the ion beam to a predetermined diameter and irradiate the sample 4 at a predetermined position at a predetermined angle. The sample 4 is heated by the heating heater 7 provided in the sample holder 5 as needed. As the ion gun of the device of the present invention, for example, a differential ion gun or the like well known to those skilled in the art is preferable.

On the other hand, the detector 3 is constructed so that its position and angle can be adjusted, and the energy distribution of the ions scattered at a predetermined angle on the surface of the sample 4 can be analyzed. The detector 3 is preferably a cylindrical mirror type energy analyzer or the like well known to those skilled in the art.

In the surface analysis apparatus of the present invention configured as described above, the ion gun 2 reduces the rare gas ions having a small mass at a predetermined angle on the surface of the sample 4 in the vacuum chamber 1 evacuated to an ultrahigh vacuum. Irradiate with accelerated energy. Sample 4
The energy distribution of the scattered ions on the surface of the detector 3
The elemental analysis and bond state analysis of the thickness of one atomic layer on the surface of the sample are performed by the analysis.

Further, the surface of the sample 4 is irradiated with a large amount of rare gas ions from the ion gun 2 to perform analyzes with different resolutions, one atomic layer on the surface is removed, and a new atomic layer is exposed. The atomic layer is then irradiated with rare gas ions with a small mass for analysis. Of course, by adjusting the acceleration energy, it is possible to perform analysis only with rare gas ions having a large mass, or to remove only one atomic layer on the sample surface by sputter etching. By repeating these operations, elemental analysis, bond state analysis, and crystal structure analysis can be performed in the depth direction from the surface of the sample in atomic layer units. Further, by performing the analysis while scanning the rare gas ion beam or by changing the incident angle of the rare gas ion beam, it is possible to perform the analysis without missing a minute portion of the sample surface. As a result, the above-mentioned analysis can be performed accurately even if the portion where sputter etching is performed is limited to an extremely small area on the sample surface.

Using the surface analyzer of the present invention, the termination surface of the Y ₁ Ba ₂ Cu ₃ O _{7 -X} oxide superconductor thin film surface was analyzed by the method of the present invention. Y ₁ Ba ₂ Cu ₃ O _7-X is known to be a secondary crystal having a crystal structure of a perovskite structure. The sample used was a substantially single crystal Y film with a thickness of 100 nm formed on the SrTiO ₃ substrate by the reactive co-evaporation method.
₁ Ba ₂ Cu ₃ O _7-X thin film. SrTiO formed with this thin film
_{The three} substrates were fixed to the sample holder 5 of the vacuum chamber 1 shown in FIG. 1 via the ultrahigh vacuum transfer path.

Next, the inside of the vacuum chamber 1 is set to 1 × 10 ^-10 Torr.
It was evacuated to, and the surface was analyzed by irradiating the sample with a He ion beam of 0.5 keV from the ion gun 2. The analysis results are shown in FIG. The graph of FIG. 2A is a graph showing the energy distribution (spectrum) of scattered He ions. Figure 2
As can be seen from the graph in (a), the sample Y ₁ Ba ₂ Cu ₃ O _7-X
The surface of the thin film has many scattered ions with energies corresponding to Cu atoms and O atoms. As a result, the sample Y ₁ Ba ₂ Cu ₃ O
The top layer of the _7-X thin film was found to be the Cu-O plane.

Next, the sample was irradiated with a 0.5 keV Ne ion beam from the ion gun 2 at a dose of about 10 ¹⁴ / cm ² to partially remove one atomic layer (Cu-O surface) on the sample surface. Exposed atomic layer. This sample was irradiated again with He ions of 0.5 keV to analyze the surface. The analysis results are shown in Fig. 2 (b).
The graph of FIG. 2B is a graph showing the energy distribution (spectrum) of He ions scattered in the second analysis. As can be seen from the graph in Fig. 2 (b), scattered ions with energies corresponding to Cu atoms and O atoms are also large on this newly exposed surface, but scattered ions with energies corresponding to Cu atoms decrease and Ba The scattered ions of the energy corresponding to are increasing.

Again, the sample was irradiated with a 0.5 keV Ne ion beam from the ion gun 2 at a dose of about 10 ¹⁴ / cm ² to further remove one atomic layer on the surface of the sample and expose a new atomic layer. This sample was irradiated again with He ions of 0.5 keV to analyze the surface. The analysis results are shown in FIG. 2 (c). The graph in FIG. 2C is a graph showing the energy distribution (spectrum) of He ions scattered in the third analysis. As can be seen from the graph in FIG. 2 (c), scattered ions with an energy corresponding to Ba atoms are the most on this newly exposed surface.
As a result, it was found that the second layer of the Y ₁ Ba ₂ Cu ₃ O _7-X thin film of the sample was composed of Ba.

It is known that the Cu-O face of a Y ₁ Ba ₂ Cu ₃ O _7-X oxide superconductor has the following three types of terminations: (1) Cu (1) -O chain (2) Cu (2) -O ₂ surface on Y atom along c direction (3) Cu (2) -O ₂ surface on Ba atom Further, the present inventors only formed a film ( It was confirmed that the number of scattered ions having energy corresponding to O atoms on the surface of the as-deposited Y ₁ Ba ₂ Cu ₃ O _7-X oxide superconducting thin film was reduced by heat treatment at 500 ° C. for 5 minutes. From the above, the sample Y
_Since Ba exists in the lower layer of the surface of the ₁ Ba ₂ Cu ₃ O _7-X thin film and oxygen is easily lost, the surface of the Y ₁ Ba ₂ Cu ₃ O _7-X thin film of the sample has a Cu-O chain structure. I found that it was terminated with.

During the above analysis, the pressure in the vacuum chamber 1 was maintained at 1 × 10 ^-10 Torr and each step was carried out continuously.

When the method of the present invention is applied to the production of a laminated film, it is possible to produce a laminated film in which the surface condition of the lower thin film is partially different depending on the location. For example, when stacking an upper thin film on a SrTiO ₃ thin film, a place for forming the upper thin film on the Sr—O layer and a place for forming the upper thin film on the Ti—O layer can be selected. . In addition, when forming an upper thin film on the Y ₁ Ba ₂ Cu ₃ O _7-X oxide superconducting thin film, Cu (1)-
It is possible to arbitrarily select whether to form the upper thin film on any of the O chain, the Ba surface, and the Cu (2) -O ₂ surface.

[0026]

As described above, according to the present invention,
Provided are a method capable of analyzing the surface of a sample for each atomic layer in the depth direction, and an apparatus for realizing the method. According to the method of the present invention, since the analysis is performed by irradiating the ion beam having a small energy and a small mass, it is possible to perform an accurate analysis with almost no damage to the sample surface. Further, since the sample surface is removed by the ions having relatively small energy, 1
Can be precisely removed atomic layers at a time. Furthermore, since the treatment is continuously performed under ultra-high vacuum, accurate analysis is possible without contaminating the newly exposed surface with high potential, and it is also possible to form a laminated film using this surface. Is.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of the surface analysis apparatus of the present invention for carrying out the method of the present invention.

FIG. 2 is a graph showing the results of analysis performed by the method of the present invention using the apparatus of the present invention.

[Explanation of symbols]

 1 vacuum chamber 2 ion gun 3 detector 4 sample 5 sample holder 6 manipulator 7 heater 10 exhaust port

Claims (11)

[Claims] 1. A method of injecting a low-energy ion beam into a sample, measuring the energy distribution of scattered ions, and analyzing the sample, in which a rare gas ion with a small mass is injected into the sample under high vacuum. , The process of analyzing the sample surface,
A process of injecting rare gas ions with a large mass into the sample and removing the sample surface by sputter etching for each atomic layer thickness, and again injecting a rare gas ion with a small mass into the sample to analyze the sample surface And a surface analysis method. 2. The surface analysis method according to claim 1, wherein beams of two or more kinds of rare gas ions having different masses are incident on the sample to perform analysis with different resolutions. 3. Analysis of the sample surface by measuring the energy distribution of the rare gas ions scattered on the sample surface when the beam of the large-mass rare gas ions is incident on the sample and the sample surface is sputter-etched. The surface analysis method according to claim 1 or 2, which is also performed. 4. The surface analysis method according to claim 1, wherein the rare gas ion beam is focused with a small diameter for analysis. 5. The analysis is performed by scanning the rare gas ion beam relative to a sample.
5. The surface analysis method according to any one of 4 to 4. 6. The surface analysis method according to claim 1, wherein the analysis is performed while changing the incident angle of the rare gas ion beam with respect to the sample. 7. The method according to claim 1, wherein each step of injecting the rare gas ions into the sample is performed under an ultrahigh vacuum of 1 × 10 ⁻⁹ Torr or more. Surface analysis method. 8. The surface analysis according to claim 1, wherein each of the rare gas ions is incident on a sample at an energy of 1 keV or less to perform analysis and / or sputter etching. Method. 9. A vacuum chamber whose inside can be evacuated to a high vacuum, and an ion beam which is provided in the vacuum chamber and is accelerated to a predetermined energy of two or more kinds of rare gas ions having different masses. A surface analysis apparatus, comprising: an ion source configured to be incident on the sample at a predetermined angle; and a measuring unit that measures an energy distribution of ions scattered by the sample. 10. A means for focusing the ion beam to a predetermined diameter is provided, and the measuring means is configured to be capable of measuring the energy distribution of the ions scattered in a predetermined angular range. 7. The surface analysis device according to 7. 11. The position of the sample is set to 3 of x, y and z.
It can be changed in the axial direction and the tilt angle of the sample is different.
The surface analysis device according to claim 7, further comprising a manipulator that can be changed about an axis.