JP3188393B2 - Multilayer spectroscopy element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer spectroscopic element in which a plurality of sets of reflective layers made of heavy elements and spacer layers made of light elements are alternately stacked, and more particularly to a reduction in the background.

[0002]

2. Description of the Related Art An example of an X-ray fluorescence analyzer is shown in FIG.
In the figure, a sample 2 is irradiated with a primary X-ray B1 from an X-ray tube 1, and a fluorescent X-ray B2 generated in the sample 2 is diffracted by a multilayer spectroscopic element 3, and The diffracted X-rays B3 are made incident on the detector 4, and the analyzer 6 obtains an analytical peak profile of the X-rays to be diffracted. The solar slit 5 is for converting X-rays into parallel light.

In this type of X-ray fluorescence spectrometer, an element having a relatively large atomic number such as Fe, Ni, Mo or W is used as a soft X-ray multilayer spectroscopic element having a wavelength of about 10 to 120 (１２０). A multilayer film is used in which a plurality of sets of reflective layers including a plurality of sets of reflective layers and spacer layers including elements having relatively small atomic numbers such as Be, B, C, B ₄ C, or Si are alternately stacked. However, when the multilayer spectroscopic element is used as it is, the background X-ray having a wavelength close to the X-ray to be diffracted is totally reflected mainly by the upper reflective layer of the multilayer spectroscopic element and becomes a background component. Background (b) against the Bragg reflection peak (p)
In the ratio p / b. For this reason, especially in quantitative X-ray fluorescence analysis of trace elements, the analysis accuracy is greatly affected.

As a countermeasure for reducing the background, reflection of visible light and ultraviolet light has been conventionally suppressed by providing a carbon film of about 5000 (Å) having a low reflectance to the outermost surface on the outermost surface. X-ray multilayer mirror (Japanese Unexamined Patent Publication No.
No. 48399), and a soft X-ray multilayer mirror which is hardly totally reflected by making the surface of the multilayer film inclined with respect to the reflection surface in the multilayer film for soft X-rays ( JP-A-4-301600) Soft X-rays in which the surface of the multilayer film is not parallel to the laminating surface of the multilayer film, such as a concavo-convex shape, so as to be hardly totally reflected with respect to the soft X-rays. Multilayer film spectroscopic element
No. 6296) has been proposed.

[0005]

However, when a carbon film of about 5,000 (Å) is provided on the surface of the multilayer film, the influence of absorption becomes remarkable even for soft X-rays to be analyzed. There was a problem that the strength was reduced to less than half.

In the case where the multilayer film surface is inclined with respect to the reflection surface of the multilayer film, it is extremely difficult to form the multilayer film surface at a predetermined inclination without damaging the multilayer film body. In addition, even when a thin film having a wedge-shaped cross section is formed on the surface, in order to obtain an effective inclination, the thickness of the film itself becomes extremely large, and the analysis intensity due to the absorption effect is increased. However, there was a problem such that the number of the samples decreased sharply.

Further, when the surface of the multilayer film is not parallel to the laminated surface of the multilayer film, such as an uneven shape,
There is a problem that surface processing of such a multilayer film is very difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a multilayer spectroscopic element capable of easily reducing a background X-ray having a wavelength close to the X-ray to be diffracted.

[0009]

According to one aspect of the present invention, a reflective layer and a spacer layer containing an element having an atomic number smaller than that of the element forming the reflective layer are provided. In a multilayer spectroscopic element configured by alternately stacking a plurality of sets and diffracting incident X-rays to generate diffracted X-rays,
An interference layer containing an element having an atomic number smaller than the element forming the reflective layer is formed on the surface where the X-rays are incident, and the thickness of the interference layer is such that the background X-ray has a thickness at the surface of the interference layer. And the reflected X-rays from the uppermost reflective layer are set to cancel each other.

According to the above configuration, the thickness of the interference layer is set so that the background X-rays have a phase in which the reflected X-rays on the surface of the interference layer and the reflected X-rays from the uppermost reflective layer cancel each other. Is set to Therefore, the background X-ray overlapping the Bragg reflection peak of the X-ray to be diffracted included in the incident X-ray is suppressed, and the ratio of the background (b) to the Bragg reflection peak (p) is p / b.
, And accurate quantitative analysis of X-rays to be diffracted becomes possible.

Preferably, an element forming the spacer layer and an element forming the interference layer are the same. Thereby, only two types of elements are required, and the manufacture of the multilayer spectroscopic element is facilitated.

[0012] Preferably, the interference layer is an X-ray diffraction target.
It is made of a material having an absorption edge at a wavelength slightly shorter than the wavelength of the line. Thus, the intensity of the X-ray of the diffraction object that has passed through the interference layer does not decrease, and the spectral performance of the multilayer spectral element does not decrease.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a longitudinal sectional view showing the structure of the multilayer spectral element 3 according to one embodiment of the present invention.
The multilayer spectroscopic element 3 includes a reflection layer 31 and the reflection layer 3.
A large number of layer pairs including a spacer layer 32 containing an element having an atomic number smaller than the element forming element 1 are stacked on the substrate 7. For example, the reflection layer 31 includes an element having a relatively large atomic number, and the spacer layer 32 includes the reflection layer 31.
Contains an element having an atomic number smaller than that of the element forming. In this embodiment, tungsten (W) is used for the reflective layer 31 and carbon (C) is used for the spacer layer 32, and the uppermost layer of the layer pair is the reflective layer 31. The multilayered spectral element 3 of this embodiment has a 50-layer pair and a period length d = 50.
Å, the film thickness ratio W: C = 1: 2. The multilayer spectroscopy element 3 diffracts the incident light beam B2 to generate a diffracted X-ray B3.

A light element, a light element,
For example, an interference layer 33 made of carbon (C) is formed. The thickness D of the interference layer 33 is equal to the background X
With respect to the line B22, the phase is set such that the reflected X-ray B31 totally reflected on the surface S1 of the interference layer 33 and the reflected X-ray B32 totally reflected on the uppermost layer S2 of the reflecting layer 31 cancel each other out. The thickness D of the interference layer 33 is set to several tens to several hundreds of degrees, and in this embodiment, a carbon film having a thickness of about 35 degrees is formed.

In this embodiment, the interference layer 33 is formed on the reflective layer 31, which is the uppermost layer of the layer pair. However, when the uppermost layer of the layer pair is the spacer layer 32, The total thickness of the interference layer 33 and the thickness of the interference layer 33 is D.

The material of the interference layer 33 includes X to be diffracted.
It is preferable to use a substance having an absorption edge at a wavelength slightly shorter than the wavelength of the line B21, that is, a light element having a small absorption coefficient for the X-ray B21 to be diffracted. Therefore, since the X-ray B21 to be diffracted is not absorbed by the interference layer 33, the intensity of the X-ray B21 is not reduced, and the spectral performance of the multilayer film spectral element 3 is secured.

In this embodiment, tungsten (W) is used for the material of the reflection layer 31 and carbon (C) of the same element is used for the materials of the spacer layer 32 and the interference layer 33. As described above, by using the same material for the spacer layer 32 and the interference layer 33, only two kinds of elements, tungsten (W) and carbon (C), are required, and the manufacture of the multilayer film spectral element 3 is facilitated. . However, the types of elements of each of the layers 31 to 33 are not limited to this, and the elements of the spacer layer 32 and the interference layer 33 may not be the same. Each layer 31-33
It is preferable to use, as other combinations of the elements constituting the above, for example, those selected and combined appropriately from the following elements or compounds depending on the purpose and application. Reflective layer 31: Cr, Fe, Ni, Mo, Ru, Rh, W, Re spacer layer 32: Be, B, C, B 4 C, Si, Sc interference layer 33: Be, B, C, B 4 C, Al, Si, Sc

The multilayer film spectroscopic element 3 is formed by a film forming method such as sputtering, vacuum evaporation, and CVD.

The operation of X-ray fluorescence analysis using the multilayer spectroscopy device 3 of FIG. 1A will be described below. For example, using lithium fluoride (LiF) for the sample S in FIG.
Mg-Kα fluorescent X-ray analysis is performed on magnesium impurities contained in.

When the primary X-ray B1 generated by the X-ray source 1 shown in FIG. 3 is irradiated on the sample S, a secondary (fluorescent) X-ray B2 unique to the sample S is generated, and the secondary X-ray B2 is multi-layered. Diffracted by the film spectral element 3. As shown in FIG. 1A, the secondary X-ray B2 includes, in addition to the Mg-Kα fluorescent X-ray B21 to be diffracted, the F-Kα fluorescent X-ray B22 which is a background X-ray having a wavelength close thereto. It is included. Among them, Mg-Kα fluorescent X
The line B21 undergoes Bragg reflection only when the incident angle θ to the multilayer film spectroscopic element 3 matches a certain angle determined by the X-ray wavelength λ and the lattice spacing 2d of the element, thereby generating a diffracted X-ray B3. . This is given by the well-known Bragg equation shown in the following equation (1). 2d · sin θ = nλ (where n is the order of reflection 1, 2, 3,...) (1)

At this time, the F-Kα fluorescent X-ray B22 is also incident at an incident angle θ, and the reflected X-ray B31 at the surface S1 of the interference layer 33 formed on the surface of the multilayer spectroscopic element 3 is totally reflected at the reflection angle θ. The reflected X-rays B32 reflected from the uppermost surface S2 of the reflective layer 31 are also totally reflected at the reflection angle θ. In this case, the reflection layer 31
When the thickness of the interference layer 33 is set to D, the reflected X-ray B32 reflected from the interference X-ray B32 is shifted by 2D sin θ by the path length compared to the reflected X-ray B31 from the interference layer 33. Reflected light beam B31,
The waveform of B32 is shown in FIG. In this figure, λ
a indicates the wavelength of the reflected light beams B31 and B32.

Here, the thickness D of the interference layer 33 shown in FIG.
Is reflected X-rays B3 from the interference layer 33 shown in FIG.
1 and the waveform of the reflected X-ray B32 from the reflective layer 31 are 180 ° on the same plane P orthogonal to the reflected optical path.
Are set to have a phase difference of
B32 interferes and cancels each other. That is, the interference layer 33 formed on the surface of the multilayer spectral element 3
Causes a phase shift such that the reflected X-rays B31 and the reflected X-rays B32 have opposite waveforms.
This corresponds to 2D · sin θ = nλ corresponding to the above equation (1).
a, nλa on the right side is λλa, 3 / 2λa,
5 / 2λa,...
Is set.

Thus, the background X-ray FK
The α fluorescent X-ray B22 is removed or reduced. Then, the analyzer 6 obtains an Mg-Kα fluorescent X-ray analysis peak profile of the diffraction object.

FIG. 2A shows a case where an interference layer 33 is formed on the surface of the multilayer film spectroscopic element 3, and FIG.
Respectively, when lithium fluoride (L
8 shows a Mg-Kα fluorescent X-ray analysis peak profile for a magnesium impurity in iF). FIG. 2 (a),
In (b), the horizontal axis represents the incident angle θ of X-rays to the multilayer film spectroscopic element 3, and the vertical axis represents the reflectivity, which is the reflected (diffraction) X-ray intensity I _R with respect to the incident X-ray intensity I ₀ . Show. In the Bragg reflection peak of the Mg-Kα fluorescent X-ray which is the X-ray to be diffracted, the F-Kα fluorescent X-ray which is the background X-ray is present as shown in FIG. ) Are removed as shown in FIG. Moreover, the peak intensity of the Mg-Kα fluorescent X-ray in (a) is
Compared to (b), there is almost no change, and the influence of the interference layer 33 on the peak intensity can be ignored.

Thus, the Mg-Kα fluorescence X to be diffracted is
F-Kα fluorescent X-rays of background X-rays overlapping the Bragg reflection peaks of the X-rays are largely removed, and the ratio of the background (b) to the Bragg reflection peak (p) p / b
, And accurate quantitative analysis of Mg-Kα fluorescent X-rays becomes possible.

The same effect as above can be obtained by using ruthenium (Ru).
X-ray fluorescence analysis of boron (B) -containing thin film and the like on a silicon substrate using a Ru / B ₄ C multilayer film spectroscopic element in which a plurality of sets of reflective layers and B ₄ C spacer layers are alternately laminated. It is also obtained when performing. In this case, the Si-L fluorescent X
The line becomes the background X-ray. As described above, the interference layer having a thickness that cancels out the background X-rays on the surface of the multilayer spectral element is made of B ₄ C, which is the same material as the spacer layer, or one of the elements contained in the spacer layer. It is preferably formed by a part B or C. B
_{When the} interference layer made of ₄ C was used, the ratio p / b of the background (b) to the Bragg reflection peak (p) was 80 when the interference layer was not provided. To 110.

In this embodiment, the multilayer film spectroscopic element 3 is used for X-ray fluorescence analysis. However, the present invention is not limited to this, and is widely used for soft X-ray spectroscopy including diffraction X-ray analysis. be able to.

[0028]

According to the present invention, the thickness of the interference layer formed on the surface of the multilayer spectroscopic element is determined by the difference between the background X-ray and the reflection X-ray on the surface of the interference layer and the reflection from the uppermost reflection layer. The phase is set so that the reflected X-rays cancel each other. Therefore, the background X-ray overlapping the Bragg reflection peak of the X-ray to be diffracted included in the incident X-ray is suppressed, and the ratio p / b of the background (b) to the Bragg reflection peak (p) increases. In addition, accurate quantitative analysis of X-rays to be diffracted can be performed.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing a multilayer spectral element according to an embodiment of the present invention, and FIG. 1B is a view showing a waveform of a reflected X-ray.

FIG. 2 is a characteristic diagram showing a fluorescent X-ray analysis peak profile, wherein (a) shows a case having an interference layer, and (b) shows a case without an interference layer.

FIG. 3 is a side view showing an X-ray fluorescence spectrometer using a multilayer spectroscopic element.

[Explanation of symbols]

3: Multilayer spectroscopic element, 31: reflective layer, 32: spacer layer, 33: interference layer, B21: X-ray to be diffracted, B22:
Background X-rays, B31, B32 ... reflected X-rays.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-61-89547 (JP, A) JP-A-4-301600 (JP, A) JP-A-6-27297 (JP, A) JP-A-5-205 66296 (JP, A) JP-A-6-148399 (JP, A) JP-A-3-38602 (JP, A) JP-A-63-305299 (JP, A) JP-A-3-75600 (JP, A) JP-A-63-284499 (JP, A) JP-A-4-232900 (JP, A) U.S. Pat. No. 5,082,211 (US, A) WO 96/34274 (WO, A1) (58) Fields investigated (Int. . ^7, DB name) G21K 1/06 G01N 23/223

Claims (3)

(57) [Claims] 1. A structure in which a plurality of sets of a reflective layer and a spacer layer containing an element having an atomic number smaller than that of the element forming the reflective layer are alternately stacked, and diffracted incident X-rays to form diffracted X-rays. In the multilayer spectroscopic element to be generated, an interference layer containing an element having an atomic number smaller than the element forming the reflection layer is formed on a surface on which the X-rays are incident. For background X-rays having a wavelength close to the X-rays to be diffracted included in the above, the reflected X-rays on the surface of the interference layer and the reflected X-rays from the uppermost reflective layer cancel each other out. A multilayer spectroscopic element, characterized by being set. 2. The multilayer spectral element according to claim 1, wherein an element forming the spacer layer is the same as an element forming the interference layer. 3. The multilayer spectral element according to claim 1, wherein the interference layer is made of a material having an absorption edge at a wavelength slightly shorter than the wavelength of the X-ray to be diffracted.