JPH06109671A - X-ray analyzer and total reflection fluorescent x-ray analyzer - Google Patents

Abstract

PURPOSE:To reduce background and improve analysis accuracy by providing an X-ray half mirror for totally reflecting a part of X-rays to reduce X-ray components having longer wavelength and to allow X-rays having shorter wavelength to transmit. CONSTITUTION:An X-ray half mirror 20 is provided on a light path of X-rays B1 to totally reflect a part B11 of the X-rays B1 to reduce a part of the X-rays B11 with a long wavelength and to allow X-rays B2 with a short wavelength to transmit. The X-rays B1 incident to an artificial multi-layer film lattice 1 are diffracted on a reflecting face 1a to be monochrome. Since the reflecting face 1a forms a gentle recess, the X-rays B2 diffracted on the reflecting face 1a are incident to a light condensing point Q on a sample 2 with a small incident angle alpha. A part of the X-rays B2 are totally reflected to be reflection X-rays B4, while another part generates fluorescent X-rays B5 particular to an element constituting the sample 2. After the X-rays B5 are incident to an X-ray detector 3 and X-ray intensity is detected, a target X-ray spectrum can be obtained by a multiple wave-height analyzer 4 based on a detection signal (a).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray analyzer for elemental analysis of a sample, or to irradiate a sample surface with primary X-rays at a small incident angle to analyze fluorescent X-rays from the surface layer of the sample. The present invention relates to a total reflection X-ray fluorescence analyzer.

[0002]

2. Description of the Related Art Conventionally, a total reflection X-ray fluorescence analyzer is
It is used as a device for detecting impurities adhering to the surface layer of a sample (see, for example, JP-A-63-78056).
An example of this type of device is shown in FIG.

In FIG. 6, an X-ray B1 emitted from an X-ray source (light source) P of an X-ray tube 5 is diffracted by a curved type dispersive crystal (dispersion element) 1A through a slit 5a and diffracted by X-ray diffraction. The surface (primary X-ray) B2 is irradiated on the surface 2a of the sample 2 at a small incident angle α (for example, about 0.05 ° to 0.20 °). A part of the diffracted X-ray B2 incident on the sample 2 is totally reflected to become a reflected X-ray B4, and the other part excites the sample 2 as a primary X-ray, and fluorescence peculiar to the elements constituting the sample 2 is emitted. X-ray B
5 is generated. The fluorescent X-ray B5 is incident on the X-ray detector 3 arranged so as to face the sample surface 2a. The X-ray detector 3 detects the X-ray intensity of the incident fluorescent X-rays B5, and then the target X-rays are detected by the multiple wave height analyzer 4 based on the detection signal a from the X-ray detector 3. A spectrum is obtained.

In this type of total reflection X-ray fluorescence analyzer, since the incident angle α of the diffracted X-ray (primary X-ray) B2 is small, the reflected X-ray B4 and the scattered X-ray are transmitted to the X-ray detector 3. Fluorescent X-ray B5 which is difficult to enter and is detected by the X-ray detector 3.
There is an advantage that the noise is smaller than the output level of. That is, a large S / N ratio can be obtained, and therefore, there is an advantage that the analysis accuracy is good and, for example, even a trace amount of impurities can be detected. Therefore, this analysis method
It is effective as an analysis method of surface contamination of silicon wafers and is widely adopted.

Further, in this conventional technique, the primary X-ray B1 is monochromated by using the dispersive crystal 1A, and further, since the curved dispersive crystal 1A is used, the diffracted X-ray B2 is reflected on the sample surface 2a. There is also an advantage that the intensity of the excited X-rays is increased after being condensed, and therefore the analysis accuracy is further improved.

[0006]

By the way, if the X-ray B1 is monochromatic, the intensity of the diffracted X-ray B2 is lowered. Therefore, the solid angle (divergence angle) Ωo emitted from the X-ray source P is increased, It is desired to increase the intensity of the diffracted X-ray B2 incident on the sample 2. However, since the diffracted X-ray B2 is condensed at different incident angles α, the inclination of the optical path of the incident diffracted X-rays B2 is slightly different, and therefore the change Δα of the incident angle α also increases as the solid angle Ωo increases. growing. Here, the incident angle α needs to be set within a small angle range of about 0.05 ° to 0.20 ° as described above, and therefore the solid angle Ωo cannot be increased, and therefore the diffraction X-ray B2 The strength cannot be increased sufficiently.

Therefore, it is conceivable to use not the dispersive crystal but the artificial multilayer lattice as the dispersive element. The artificial multi-layered film grating has a multi-layered film formed on its reflecting surface. Since the period d of the lattice plane interval is larger than that of the dispersive crystal, the reflectivity of the diffracted X-ray B2 is large. By using, the intensity of the diffracted X-ray B2 becomes large.

The X-ray diffraction condition is given by the following Bragg equation, as is well known. 2d · sin θ = nλ θ: incident angle, diffraction angle λ: wavelength of X-ray n: order of reflection Here, since the artificial multilayer film lattice has a large lattice spacing d, as described above, the Bragg equation As can be seen from, the incident angle θ becomes smaller. Therefore, the X-ray B1 having a long wavelength is totally reflected on the surface of the artificial multilayer film grating, and the continuously reflected continuous X-rays enter the sample 2 together with the diffracted X-ray B2.
As described below, the continuous X-rays having a long wavelength serve as a background of the characteristic X-rays (fluorescent X-rays) of the analysis element and reduce the resolution (S / N ratio). The drawback is that impurities cannot be accurately analyzed.

In FIG. 7, the diffracted X-ray B2 is the W-Lβ _1- ray, the characteristic X-ray (fluorescent X-ray) of the analytical element is the Ti-Kα-ray, and the Fe-
The relationship between the wavelength of the detected X-ray and the X-ray intensity in the case of the Kα ray and the Ni-Kα ray is shown. As can be seen from this figure, the characteristic X-ray B5 of the analytical element is more than the diffracted X-ray B2.
₁ towards a long wavelength, therefore, a long continuous X-ray B5 ₂ wavelengths incident on the sample 2 with the diffraction X-ray B2 unique X-ray B
5 ₁ and overlaps, the background. as a result,
This leads to a decrease in analysis accuracy.

Such a problem occurs not only in the total reflection X-ray fluorescence analysis but also in other X-ray analyzers and the like.

The present invention has been made in view of the above conventional problems, and in an X-ray analyzer such as a total reflection X-ray fluorescence analyzer, the X-ray having a long wavelength is removed to reduce the background. The purpose is to improve the analysis accuracy.

[0012]

In order to achieve the above object, an X-ray analysis apparatus and a total reflection X-ray fluorescence analysis apparatus of the present invention are provided with an artificial multilayer film grating as a spectroscopic element, A half mirror for X-rays is inserted in the optical path of the X-rays to totally reflect a part of the X-rays to reduce the component of the X-rays having a long wavelength and to transmit the X-rays having a short wavelength.

[0013]

According to the present invention, the half mirror for X-rays totally reflects a part of X-rays and reduces the component of X-rays having a long wavelength. X-rays can be removed, thus reducing background components. On the other hand, since X-rays having a short wavelength pass through the X-ray half mirror, the intensity of X-rays diffracted by the artificial multilayer film grating is hardly reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The first embodiment shown in FIGS. 1 to 4 is applied to a total reflection X-ray fluorescence analyzer. In FIG. 1, in the irradiation device, an X-ray half mirror 20 is inserted in the optical path of the X-ray B1 between the X-ray source 5 and the artificial multilayer film grating 1. This X-ray half mirror 20 is designed so that X from the X-ray source P
A part B11 of the line B1 is totally reflected as shown by a chain line to reduce the component of the X-ray B11 having a long wavelength and transmit the X-ray having a short wavelength. This X-ray half mirror 20 is made of, for example, polypropylene (density: about 1 g /
cm ³ ) and polyester (density: about 1.3 g / c
Reflective surface 2 of resin film with low density (specific gravity) like m ³ )
0a is provided with a coating (thickness: 200Å) made of a light metal such as aluminum.

In this embodiment, as described later, the divergence angle Ω
o is set to about 1 °, and the X-ray half mirror 20 has a log spiral shape (logarithmic spiral) in order to keep the incident angle β of the X-ray B1 incident on the X-ray half mirror 20 in FIG. Bent). The incident angle β to the X-ray half mirror 20 is set to, for example, about 0.22 ° when Ti, Fe and Ni are used as analysis elements.
In the log-spiral half mirror 20 for X-rays, the shape of the reflecting surface 20a of the half mirror 20 for X-rays is determined by the following equations (1) and (2).

[0016]

[Equation 1]

The artificial multilayer grating 1 shown in FIG. 1 is an X-ray source P.
The X-ray B1 incident at the incident angle θ is diffracted at the reflection surface 1a at the diffraction angle θ to be monochromatic. The period d of the lattice plane spacing in the artificial multilayer film lattice 1 is set to continuously increase along the surface of the reflecting surface 1a.
In relation to the X-ray source P, the cycle d is set to be larger as the distance from the X-ray source P increases as indicated by an arrow 10.
For example, the length of the artificial multilayer lattice 1 in the direction of arrow 10 is 4
Assuming 0 mm, d = 50Å is set at the left end 1L and d = 72Å at the right end 1R.

In the artificial multilayer film lattice 1, the reflecting surface 1a is formed by a gentle concave surface. The diffracted X-ray B2 diffracted by the reflecting surface 1a has a small incident angle α (for example, 0.05 ° to
It is incident on the condensing point Q on the sample (for example, a silicon wafer) 2 at 0.20 °. Incident diffracted X-ray (excited X-ray) B2
Partially is totally reflected to become a reflected X-ray B4, and the other part excites the sample 2 to generate a fluorescent X-ray B5 peculiar to the element constituting the sample 2. The fluorescent X-ray B5 is incident on the X-ray detector 3 arranged so as to face the sample surface 2a. The X-ray detector 3 detects the X-ray intensity of the incident fluorescent X-rays B5, and then the target X-rays are detected by the multiple wave height analyzer 4 based on the detection signal a from the X-ray detector 3. A spectrum is obtained.

In the above structure, the X-ray half mirror 20 is the X-ray B having the long wavelength among the X-rays B1 from the X-ray source P.
The X-ray B1 from which the component of the X-ray B11 having a long wavelength is reduced or removed is totally incident on the artificial multilayer film grating 1 as shown by a dashed-dotted line. Therefore, even if the artificial multilayer film grating 1 that may totally reflect X-rays with long wavelengths is used, the excited X-rays (diffracted X-rays) B2 hardly contain long wavelength components. Therefore, even X-ray detector 3, since the continuous X-rays B5 ₂ of FIG. 7 does not enter most analytical accuracy is significantly improved.

By the way, in the total internal reflection X-ray fluorescence analyzer, since the incident angle α in FIG. 1 is set to a very small angle as described above, the incident angle α (0.05
It must be set smaller than the range (° to 0.2 °).
Here, in the conventional curved crystal 1A of FIG. 6, since the convergence angle Ω and the divergence angle Ωo are equal to each other, the divergence angle Ωo needs to be small (for example, 0.1 °). The intensity of the X-ray (diffracted X-ray) B2 becomes weak. On the other hand, in this embodiment, the period d of the lattice plane spacing in the artificial multilayer film lattice 1 of FIG. 1 is X along the surface of the reflecting surface 1a.
Since it is continuously set to be larger as the distance from the radiation source P increases, the divergence angle Ωo becomes larger than the convergence angle Ω as described below, and therefore, the intensity of the excitation X-ray (diffraction X-ray) B2 can be increased.

The X-ray diffraction condition is given by the Bragg equation described above. If the angle formed by the incident X-ray B1 and the diffracted X-ray B2 (hereinafter referred to as “reflection angle”) is Ψ _N , the Bragg equation is expressed by the following equation (3). 2d · sin {(π−Ψ _N ) / 2} = nλ (3) Further, this equation (3) can be converted into the following equation (4). 2d · cos (Ψ _N /2)=nλ...(4)

From the equation (4), when the period d becomes large, that is, at the reflection point far from the X-ray source P in the artificial multilayer film lattice 1, the reflection angle Ψ _N becomes large and Ψ ₁ <Ψ ₂ . Now, focusing on ΔPLO and ΔQRO, the corner LOP
= Angle ROQ and Ψ ₁ <Ψ ₂ , the convergence angle Ω becomes smaller than the divergence angle Ωo. Therefore, the X-ray B1 emitted toward the artificial multilayer film lattice 1 with a large divergence angle Ωo (for example, 1 °) is converted into a small convergence angle Ω (for example, 0.1).
Since the light can be incident on the sample 2 at an angle of °), it is possible to suppress the decrease in the intensity of the diffracted X-ray B2 and increase the intensity as compared with the conventional case. As a result, analysis accuracy is improved.

Next, a method of determining the period d of the lattice plane spacing of the artificial multilayer film lattice 1 will be described. First, the incident angle α and the convergence angle Ω are determined based on the range exhibiting the phenomenon of total reflection, and the wavelength λ of the monochromatic light (diffracted X-ray) B2 to be used is determined.
To decide. Next, the reflection angles Ψ ₁ and Ψ ₂ at both ends of the artificial multilayer film grating 1 are determined, and the periods d ₁ and d ₂ at the L point and the R point at both ends are determined. Between the L point and the R point, the value of the incident angle θ in the Bragg's equation is generally small. Therefore, if it is changed approximately linearly, the diffracted X-ray B2 can be converted to the condensing point Q with sufficient accuracy. Converge.

Next, an example of a method of manufacturing the above-mentioned artificial multilayer film lattice 1 will be described with reference to FIG. First, for example, a substrate 1b having a flat surface such as a silicon wafer is prepared, and a vapor deposition base material 6w made of tungsten and a vapor deposition base material 6 made of silicon are provided immediately below the right end 1R thereof.
install si. Subsequently, as shown in FIG. 3A, the tungsten vapor deposition base material 6w is evaporated in a vacuum to form the base material 1b.
A tungsten thin film 1w is formed on the surface of. Then,
As shown in FIG. 3B, the silicon evaporation substrate 6si is evaporated in a vacuum, and the silicon thin film 1si is vacuum evaporated on the tungsten film 1w. By alternately repeating the vapor deposition of tungsten and silicon, the artificial multilayer film lattice 1 of FIG. 3C is obtained.

Here, since the vapor deposition base materials 6w and 6si shown in FIGS. 3A and 3B are both installed right below the right end 1R, the thin films 1w and 1si become thicker at the right end 1R. ,
It becomes thinner at the left end 1L. Therefore, as shown in FIG. 3C, the period d of the lattice spacing becomes continuously larger along the surface of the reflecting surface 1a as it goes to the right. Although the reflecting surface 1a is slightly convex, the artificial multilayer film grating 1 is bent to make it a flat surface or a concave surface, if necessary.

Next, another example of the method for manufacturing the artificial multilayer film lattice 1 will be described with reference to FIG. This example uses a method called Chemical Vapor Deposition,
Only the main points will be described. In FIG. 4, a mask 7 having minute slits 7a is installed on the lower surface of a substrate 1b made of a silicon wafer so as to be horizontally movable. Mask 7
A gas mixture of a gallium Ga compound and an arsenic As compound is sealed in the gas chamber 8 below. While the mask 7 is gradually moved to the left side and the gas chamber 8 is exhausted, a compound of indium In is supplied to the gas chamber 8. As a result, a thin film is formed from atoms having different diameters, and the ratio of gallium to indium in the In-Ga-As compound attached to the substrate 1b gradually changes from the right end 1R to the left end 1L (InxGa _{1 -X} As), and the period d of the lattice plane spacing at the right end 1R becomes larger than the period d at the left end 1L, for example.

By the way, in the above embodiment, the X-ray half mirror 20 of FIG. 1 was inserted in the X-ray optical path between the X-ray source P and the artificial multilayer film grating 1. However, in the present invention, as in the second embodiment of FIG. 5, the X-ray half mirror 20 is inserted in the optical path of the diffracted X-ray B2 between the artificial multilayer film grating 1 and the sample 2, for example, to diffract the X-ray. X2 with long wavelength of B2
The component of 1 may be totally reflected and reduced. In this second embodiment, since the convergence angle Ω of the diffracted X-ray B2 is extremely small, it is not necessary to bend the X-ray half mirror 20 into a log spiral shape, and therefore, the reflecting surface of the X-ray half mirror 20. 20a is formed in a planar shape.

Further, in each of the above embodiments, the period d of the lattice plane spacing of the artificial multilayer film lattice 1 of FIG. 3C is changed, but in the present invention, the period d need not be changed and may be constant. In this case, since the divergence angle Ωo in FIG. 1 is a small angle of about 0.1 °, the reflecting surface 2 of the X-ray half mirror 20 is
0a may be flat.

Further, in each of the above embodiments, the reflecting surface 20a of the X-ray half mirror 20 is coated with a metal, but the X-ray half mirror 20 used in the present invention does not necessarily require the above coating. do not do.

Further, in each of the above embodiments, the total reflection X-ray fluorescence analyzer has been described. However, the present invention relates to an X-ray analyzer having an optical system for diffracting X-rays by the artificial multilayer film grating 1. It is applicable and within the scope of this invention.

[0031]

As described above, according to the invention of claim 1, in an X-ray analyzer having an optical system for diffracting X-rays by an artificial multilayer film grating, a part of X-rays is totally reflected. Since the X-ray half mirror that reduces the long-wavelength X-ray components and transmits the short-wavelength X-rays is provided in the optical path of the X-rays, the high reflectance of the diffracted X-rays is high, but the long-wavelength X-rays are Since the defect of the artificial multilayer film lattice of total reflection can be compensated, the background component is reduced,
The analysis accuracy can be improved.

In particular, according to the second aspect of the invention, since the resolution (S / N ratio) can be increased in the total reflection X-ray fluorescence analysis used for the analysis of trace elements, the elements with extremely small concentrations can be obtained. It is also possible to analyze.

Further, according to the third aspect of the present invention, the intensity of the diffracted X-ray can be increased by changing the period of the lattice plane intervals in the artificial multilayer film lattice, so that the analysis accuracy is further improved. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a total reflection X-ray fluorescence analyzer showing a first embodiment of the present invention.

FIG. 2 is a side view showing the shape of an X-ray half mirror.

FIG. 3 is a process drawing showing an example of a method for manufacturing an artificial multilayer film lattice.

FIG. 4 is a front view showing another example.

FIG. 5 is a schematic configuration diagram of a total reflection X-ray fluorescence analyzer showing a second embodiment.

FIG. 6 is a schematic configuration diagram of a conventional total reflection X-ray fluorescence analyzer.

FIG. 7 is a characteristic diagram showing a spectrum obtained when total reflection fluorescent X-ray analysis is performed using an artificial multilayer film grating.

[Explanation of symbols]

1 ... Artificial multilayer film grating, 1a ... Reflective surface, 2 ... Sample, 2a ...
Sample surface, 3 ... X-ray detector, 20 ... X-ray half mirror, B1 ... X-ray, B11, B21 ... Long-wavelength X-ray, B
2 ... Diffracted X-ray, B21 ... Long wavelength X-ray, B5 ... Fluorescent X
Line, d ... Period, P ... X-ray source, α ... Incident angle.

Claims (3)

[Claims] 1. An X-ray analyzer having an optical system for diffracting X-rays by means of an artificial multi-layered film grating, wherein a portion of X-rays is totally reflected to reduce the components of long-wavelength X-rays and the wavelengths of which are short. An X-ray analysis apparatus, wherein an X-ray half mirror that transmits X-rays is provided in the X-ray optical path. 2. An irradiation device for diffracting X-rays by a spectroscopic element to irradiate the sample surface as primary X-rays and irradiating the sample surface with the primary X-rays at a minute incident angle, and to face the sample surface. Fluorescence X from the sample that received the primary X-ray
An X-ray detector for detecting X-rays, and a total reflection X-ray fluorescence analyzer for analyzing the X-ray fluorescence based on the detection result of the X-ray detector, wherein the spectroscopic element is an artificial multilayer film lattice. , A part of X-rays is totally reflected to reduce the component of long-wavelength X-rays, and an X-ray half mirror for transmitting short-wavelength X-rays is provided in the X-ray optical path. Reflective X-ray fluorescence analyzer. 3. An irradiation device which diffracts X-rays from an X-ray source by a spectroscopic element to collect them as primary X-rays toward the sample surface and irradiates the sample X-rays with a minute incident angle onto the sample surface. An X-ray detector for detecting fluorescent X-rays from the sample that has faced the sample surface and has received the primary X-rays, and analyzes the fluorescent X-rays based on the detection result of this X-ray detector. In the reflection fluorescence X-ray analyzer, the spectroscopic element is composed of an artificial multilayer film lattice, and the period of the lattice plane spacing in the artificial multilayer film lattice is distant from the X-ray source along the surface of the reflecting surface of the artificial multilayer film lattice. The X-ray half mirror that totally reflects a part of X-rays to reduce long-wavelength X-ray components and transmits short-wavelength X-rays is the optical path of the X-rays. It is provided in Total reflection X-ray fluorescence analyzer.