JPH0419550A - Method and apparatus for surface analysis - Google Patents

Abstract

PURPOSE:To allow the analysis of the chemical state in the microregion of even a sample weak to vacuum by maintaining a pressure difference between a vacuum chamber where the part to be installed in an ultra-high vacuum, such as X-ray source, is stowed and a vacuum chamber where the sample is installed. CONSTITUTION:The vacuum chamber 5 where the X-ray source 1 is stowed and the vacuum chamber 6 where the sample is installed are connected via an aperture 7. The vacuum chambers 5 and 6 are respectively independently evacuated to a vacuum. While the vacuum chamber 5 is maintained at the ultra-high vacuum together with the X-ray source 1, the vacuum chamber 6 is maintained at the high vacuum to the low vacuum. The pressure difference is brought between the adjacent vacuum chambers in this way and the ultra-high vacuum is maintained in the vacuum chamber 5 where the X-ray source 1, etc., are stowed in spite of the low vacuum in the vacuum chamber 6 where the sample is installed. Since there is no need for installing the sample in the ultra-high vacuum, the analysis of the chemical state on the surface of the microregion of the sample weak to the vacuum is completed in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to surface analysis of minute parts, and particularly to a surface analysis method and apparatus suitable for analyzing samples that are sensitive to vacuum.

[Conventional technology]

With the miniaturization of semiconductor devices and the appearance of various thin film devices, the need for techniques for analyzing the chemical state of microscopic parts has increased. Focusing X
XPS using rays (X-rayPhotoelec
Tron 5pectroscopy, X-ray excitation photoelectron spectroscopy) analysis technology (hereinafter referred to as 1μmXPs) is
This is the optimal microscopic chemical state analysis technology that can meet this demand.

In μmXPS, a condensing optical element is used to focus X-rays onto a minute area on a sample surface, and the kinetic energy of electrons emitted from the sample surface by X-ray irradiation is measured. In addition, to protect the X-ray source, the sample was placed in an ultra-high vacuum (<10-
Such a μ-xPS device installed in JP-A-2-25737 is disclosed.

[Problem to be solved by the invention]

In recent years, μmXPS (or xps) analysis has become a promising method for analyzing the oxygen deficiency state of oxide high-temperature superconducting thin films.

However, there was a problem that μmXPS could not be simply applied to this analysis. As mentioned above, μmXPS requires the sample to be placed in an ultra-high vacuum. On the other hand, an oxide high-temperature superconducting thin film is a sample that is sensitive to vacuum, and if it is left in an ultra-high vacuum for a long time, constituent elements will escape from the sample surface and the surface state of the sample will change. Therefore, it is necessary to perform surface analysis in a low vacuum, but conventional μm
The problem was that this was not possible from the standpoint of radiation source protection.

These concerns are not limited to oxide high-temperature superconducting thin films, but also apply to other samples (although there are differences in degree). For example, even when performing μ-xps analysis of a dry-etched sample, it is easy to imagine that if the sample is left in an ultra-high vacuum for a long time, the elements adsorbed on the sample surface will evaporate in the vacuum. can.

An object of the present invention is to provide a surface analysis method and apparatus capable of analyzing minute parts of samples that are sensitive to vacuum, including μm XPS.

[Means to solve the problem]

In order to achieve the above object, a means is provided for maintaining a pressure difference between a vacuum chamber in which a part such as an X-ray source to be placed in an ultra-high vacuum is stored and a vacuum chamber in which a sample is placed.

Possible means for maintaining the pressure difference include differential pressure exhaust using an aperture or slit, or separation of vacuum chambers using a thin film through which desired X-rays can pass. μmX
In PS, an optical system for focusing X-rays is used. When apertures and slits are used in this optical system, it is advantageous to use them also as the apertures and slits for differential pressure exhaust, since the device configuration can be made simple and compact.

The invention is described with respect to μmXPS. However, it goes without saying that the present invention is also applicable to other analytical techniques using focused X-rays (for example, X-ray microscopes and X-ray fluorescence microscopes) that have similar problems.

[Effect]

The means for maintaining the pressure differential described above provides a pressure differential between adjacent vacuum chambers. Thereby, even if the vacuum chamber in which the sample is installed is at a low vacuum, the vacuum chamber in which the X-ray source and the like are stored can be maintained at an ultra-high vacuum. As a result, there is no need to place the sample under an ultra-high vacuum, making it possible to analyze the surface of a minute area of a sample that is sensitive to vacuum.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

<Embodiment 1> FIG. 1 shows the simplest embodiment of the present invention. X-rays emitted from an X-ray source 1 are focused onto the surface of a sample 3 by an optical system 2. Electrons emitted from the surface of sample 3 by X-ray irradiation are detected by detector 4.

(or a detection whose energy is analyzed).

When light such as X-rays is emitted from the surface of the sample 3, the detector 4 is a detector for the light (or a detector that spectrally and detects the light).

A vacuum chamber 5 housing the X-ray source 1 and a vacuum chamber 6 in which a sample is placed are connected via an aperture. Further, the vacuum chambers 5 and 6 are each independently evacuated. The diameter of the aperture depends on the pumping speed of the vacuum pump that pumps out the vacuum chamber 5.6 or the degree of differential pressure pumping, but the diameter of the aperture is several inches.
φ or less is desirable.

According to this embodiment, while the X-ray source 1 is kept in an ultra-high vacuum state (that is, the vacuum chamber 1 is kept in an ultra-high vacuum state), the vacuum chamber 6 is moved from high-speed emptying to low vacuum (for example, <10 -'Pa)
As a result, analysis of a sample that is sensitive to vacuum can be completed in a short time, and changes in the surface state of the sample can be prevented.

<Example 2> In Example 1, the detector 4 was installed under high vacuum to low vacuum. However, depending on the type of detector 4, the detector 4
It may also be necessary to install the device in an ultra-high vacuum. For example, this case corresponds to the case where a detector using a nude type particle detector such as an electron multiplier or a channel plate is used as the particle detector.

FIG. 2 shows an embodiment that is effective in such a case. Second
In the figure, a detector 4 is installed within a vacuum chamber 8. The vacuum chamber 8 is evacuated independently from the vacuum chamber 6. Electrons and light emitted from the surface of the sample 3 pass through the aperture 9 and reach the detector 4. The other parts are the same as in the first embodiment.

According to this embodiment, since the detector 4 is also installed in a vacuum chamber capable of differential pressure evacuation, the degree of vacuum in the vacuum chamber 6 is
The pressure can be brought closer to atmospheric pressure compared to As a result,
Surface analysis is possible with fewer changes in the surface state of the sample.

<Example 3> In the previous example, in order to create a pressure difference between adjacent vacuum chambers, an aperture was installed to perform differential pressure evacuation. However, other means can also be used to provide this pressure difference.

An example of this case is shown in FIG. In FIG. 3, a thin film 10 is used instead of an aperture. in this case,
The thin film 10 has mechanical strength capable of withstanding a desired pressure difference,
In addition, it is necessary that it is made of a material through which the X-rays from the X-ray source 1 can pass. For example, an inorganic thin film such as Be or Mylar, or an organic thin film such as polypropylene can be used.

Furthermore, considering mechanical strength, transmittance, etc., it is considered appropriate that the thickness of the thin film is several tens of micrometers or less. The other parts are the same as in the first embodiment.

According to this embodiment, since the vacuum chambers 5 and 6 are completely isolated, the degree of vacuum in the vacuum chamber 5 can be brought closer to atmospheric pressure (the detector 4 must be installed under an ultra-high vacuum). (In such cases, the method shown in Figure 2 may also be adopted.) As a result, surface analysis can be performed with fewer changes in the surface state of the sample.

<Example 4> Depending on the size of the analysis area, a multi-stage reduction optical system may be used. In this case, the aperture installed in the middle can be used as a differential pressure evacuation aperture.

An example of this embodiment is shown in FIG.

The X-rays generated from the X-ray source 1 are transmitted to the plate 14 by the optical system 11.
The light is focused onto the aperture 15 of. This focal point becomes a light source for the optical system 12, and a reduced image thereof is created on the sample 3.

Electrons or light emitted from the surface of the sample 3 by X-ray irradiation pass through the aperture 9 and are detected by the detector 4 installed in the vacuum chamber 8 . Here, aperture 15
is an aperture for forming a light source, and at the same time is an aperture for exhausting differential pressure.

According to this example, since the aperture for forming the light source and the aperture for differential pressure exhaust can be used together, it is possible to analyze the chemical state in a more minute area with a more compact device configuration and with less change in the surface state of the sample. be.

<Example 5> Another example is shown in FIG. This example is an example in which the number of times of differential pressure evacuation is increased. The greater the number of differential pressure evacuations, the more the sample can be placed under a lower vacuum.

In FIG. 5, differential pressure evacuation is performed between the X-ray source and the optical system 11, between the optical systems 11 and 12, and between the optical system 12 and the sample 3. Correspondingly, two-stage differential pressure evacuation is also performed between the detector 4 and the sample 3 via the apertures 21 and 9. The number of stages for differential pressure evacuation can be arbitrarily set in consideration of the degree of vacuum necessary for the X-ray source 1 and the detector 4, and the degree of vacuum necessary for installing the sample 3.

According to this embodiment, since the number of differential pressure evacuation stages can be increased, the sample can be placed under a lower vacuum (that is, under a pressure closer to atmospheric pressure). As a result, surface analysis can be performed with fewer changes in the surface state of the sample.

The present invention has been described above with reference to several embodiments. The installation positions of the holes and thin films used in the previous examples can be freely changed in addition to those shown in Figures 1 to 5 depending on the purpose. One embodiment is shown in FIG.

<Embodiment 6> In FIG. 6, the aperture 24 is placed close to the optical system 22. When the aperture of the optical system 22 is small (number -)
This kind of installation is possible.

For example, if the optical system 22 is an optical system using a Walter-type reflecting mirror, the beam stop portion can be used to form an aperture for differential pressure exhaust. Further, depending on the optical system used, the optical element itself can be used as an aperture (or slit) for differential pressure exhaustion.

For example, the above-mentioned Walter type reflector, zone plate, etc. correspond to this case. Since the size of these optical elements is less than a few square centimeters, they function satisfactorily as an aperture for differential pressure exhaustion. In this case, the partition wall 25 may be provided at the position indicated by the dotted line in FIG.

Regarding the optical systems used in Examples 1 to 6, there are no particular limitations (although some mention was made in Example 6). Any optical element or optical system can be used depending on the purpose, such as a reflective type, a diffractive type, or a transmission/diffraction type.

In order to illustrate the essence of the invention, only the parts directly related to the invention are depicted in FIGS. 1-6.

Measuring the distribution of chemical states is an important issue, but the mechanism required for this is not illustrated. In order to perform distribution measurement, it is necessary to scan the sample surface with focused X-rays. A micro-drive mechanism for the sample stage and a micro-movement mechanism for the optical system necessary for this purpose can be added without affecting the present invention.

The present invention also includes device configurations in which these minute drive or movement mechanisms are added.

〔Effect of the invention〕

According to the present invention, since the sample can be placed under a lower vacuum, surface analysis can be performed with fewer changes in the surface state of the sample. As a result, micro-area chemical state analysis is possible even for samples that are sensitive to vacuum, such as oxide high-temperature superconducting thin films.

[Brief explanation of drawings]

1 to 6 are schematic vertical cross-sectional views of an analyzer according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... X-ray source, 2... Optical system, 3... Sample, 4...
...Detector, 5.6... Vacuum chamber, 7... Aperture, 8... Vacuum chamber, 9... Aperture, 10... Thin film, 11.12... Optical system, 13. ...Vacuum chamber, 14
...Plate, 15...Aperture, 16.17,18.
...Vacuum chamber, 19...Partition wall, 20゜21...Aperture, 22...Optical system, 23...Plate, famous figure λ figure bad figure figure 1 blade

Claims (1)

[Claims] 1. In surface analysis using focused X-rays, there is no pressure between the X-ray source and the sample, between the detector and the sample, or between the X-ray source and the detector and the sample. A surface analysis method that creates a difference and places the sample on the lower vacuum side. 2. The surface analysis method according to claim 1, wherein electrons or photons emitted from the sample surface by X-ray irradiation are observed. 3. The surface analysis method according to claim 2, wherein the pressure difference is created by differential pressure exhaust using an aperture or a slit. 4. Claim 2, wherein the pressure difference is formed using a thin film.
Surface analysis method described in section. 5. The surface analysis method according to claim 2, wherein the pressure difference is formed by a combination of differential pressure exhaust using an aperture or slit and a thin film. 6. The surface analysis method according to claim 2, wherein the pressure difference is created by differential pressure exhaust using a plurality of apertures or slits. 7. The surface analysis method according to items 3, 5, and 6, wherein all or part of the aperture or slit is an aperture or slit installed for collecting X-rays. 8. The surface analysis method according to claim 3, 5 or 6, wherein all or part of the aperture or slit is formed using an optical element for condensing X-rays. 9. The surface analysis method according to claims 3 to 8, wherein the surface of the sample can be scanned with the focused X-rays. 10. In a surface analysis device equipped with an X-ray generation means, a means for concentrating the X-rays onto the sample surface, and a means for detecting electrons or photons emitted from the sample surface by X-ray irradiation, A means for creating a pressure difference between the means and the sample, between the detecting means and the sample, or between the generating means and the detecting means and the sample is provided, and the sample is held in a vacuum chamber on the lower vacuum side. A surface analysis device equipped with means. 11. The surface analysis device according to claim 10, wherein the means for generating the pressure difference is differential pressure exhaust using an aperture or a slit. 12. The surface analysis device according to claim 10, wherein the means for generating the pressure difference is separation of vacuum chambers using a thin film. 13. The surface analysis device according to claim 10, wherein the means for generating the pressure difference is a combination of differential pressure evacuation using an aperture or slit and separation of vacuum chambers using a thin film. 14. The surface analysis device according to claim 10, wherein the means for generating the pressure difference is differential pressure evacuation using a plurality of apertures or slits. 15. The surface analysis device according to claim 11, 13, or 14, wherein all or part of the aperture or slit is an aperture or slit included in an X-ray focusing means. 16. The surface analysis device according to claim 11, 13, or 14, wherein all or part of the aperture or slit is an optical element included in an X-ray focusing means. 17. The surface analysis device according to items 11 to 16, comprising means for scanning the focused X-rays on the sample surface.