JPH04198745A - X-ray diffracting method - Google Patents

Abstract

PURPOSE:To reduce the effect by scattered X-rays and analyze the structure of a sample precisely and correctly by limiting the X-ray extracting angle expressed by the preset equation. CONSTITUTION:X-rays gamma generated from an X-ray source 12 are radiated to a sample 10 formed on a substrate through a solar slit 13, diffracted X-rays are extracted to analyze the crystal structure of the sample 10 in the X-ray diffracting method, and the X-ray extracting angle beta expressed by the equation beta=2theta-alpha is set to 0-5 deg., where 2theta is the diffraction angle of the sample 10 and betais the incidence angle of X-rays to the substrate. The effect by scattered X-rays caused by irregularities on the surface of the sample 10 can be reduced even when the diffraction angle 2theta of the sample 10 is 30 deg. or below, and the diffraction profile of the sample 10 can be obtained correctly with high sensitiv ity even when the sample 10 is a thin film about 100 Angstrom . The structure of the sample 10 can be analyzed precisely and correctly.

Description

[Detailed Description of the Invention] L1 Kamigorisu 1 The present invention relates to an X-ray diffraction method, and more specifically, to an X-ray diffraction method for analyzing the crystal structure of a sample such as a thin film formed on a substrate.
A related to the diffraction method.

The X-ray diffraction method is used to analyze the crystal structure of a sample. Incident X-ray diffraction methods and the like are known.

In the diffractometer method, the X-ray diffraction intensity and the diffraction angle 2θ are calculated based on the Bragg equation expressed by the following equation (1).
identify the unknown substance, determine the lattice constant,
Measures distortion, etc.

2dsinθ=n−(1) where d: lattice spacing θ·Bragg angle n: reflection order λ: wavelength of the X-ray used.

However, when measuring a thin film formed on a substrate as a sample using the diffractometer method, the 9th
As shown in the figure, since the penetration depth of the incident X 99 r is large, the diffracted X-ray d from the substrate 11 becomes the diffracted X #J! from the thin film sample 10. overlaps with d. Therefore, diffraction X-rays d from only the thin film sample 10 cannot be obtained, making it difficult to analyze the structure of the thin film sample IO.

Conventionally, when measuring the thin film sample 10 formed on the substrate 11, as shown in FIG. 1O, X#! A method has been used in which only the diffracted X-rays d from the thin film sample 10 are measured by fixing the incident angle β to a small angle of about 1 to 5 degrees and controlling the penetration depth (Y, Arnaud, M. Bru
nel et al, Applied 5urf, Sc
i.

, 26 (1986) 12). According to this method, the diffracted X-rays d from the substrate 11 can be suppressed, and the structural analysis of the thin film sample 10 can be performed with high precision.

However, in the above method, the diffraction angle 2θ is 3
0' or less, the X-ray extraction angle α is as shown in Figure 11.
becomes smaller, the scattered X-rays S generated when the incident X-rays r are scattered by the irregularities on the surface of the thin film sample 10 enter the X-ray detector, and as a result, the background intensity of the measurement profile increases and accurate measurements can be made. The problem was that it became difficult.

Furthermore, in ``Japanese Unexamined Patent Publication No. 1-167642'', by driving the scattering slit, X-ray detector, etc. parallel to the sample surface, not only the incident angle β of the incident XL9r but also the X-ray extraction angle α can be reduced. , a method of reducing the penetration depth of incident X-rays r has been proposed, but the above-mentioned problems have not been solved even in this method.

The present invention was made in view of the above-mentioned problems, and even when the diffraction angle 2θ of the sample is 30° or less, it is possible to reduce the influence of scattered The purpose is to provide an X-ray diffraction method that can perform analysis.

Steps for Solving the Problems In order to achieve the above-mentioned objects, the X-ray diffraction method according to the present invention irradiates a sample formed on a substrate with X-rays, extracts the diffracted X-rays, and extracts the diffracted X-rays from the sample. X to analyze crystal structure
In the line diffraction method, the X-ray extraction angle a expressed by β = 2θ - α (2θ: diffraction angle of the sample, β the incident angle of X-rays to the substrate) is set to be greater than 0° and less than 5°. It is a feature.

According to the method described above,
Since the beam extraction angle α is set to be greater than 0° and less than 5°, the X-ray penetration depth is kept small and the incident angle β becomes large, so that the scattered X-rays based on the incident X-rays on the sample surface are suppressed. is suppressed. Therefore, the diffraction profile of the sample can be obtained with high sensitivity and accuracy.

The present invention will be explained in detail below.

Ignoring reflection and refraction at the sample surface and interface, the dependence of the X-ray penetration depth t on the angle of incidence is expressed by the following formula (2): % μ: X-ray absorption coefficient of the sample β: Incident angle of Xla with respect to the substrate α: represents the X-ray extraction angle.

FIG. 6 shows the results of calculating the Xll penetration depth t2 using equation (2) when the X-ray extraction angle a is fixed and the X-ray incident angle β is varied. Note that the sample was Au.

As is clear from FIG. 6, when the X-ray extraction angle α is fixed, the X-ray penetration depth t is equal to the incident angle β of the X-ray on the substrate.
It changes depending on. Conversely, the X-ray penetration depth 1p is
This shows that it can be controlled by the wire take-off angle α.

On the other hand, FIG. 7 is a schematic diagram showing the situation when the surface of the sample 10 is irradiated with incident X tra r at the same angle as the critical angle β0 of total reflection. is rP, Wobra
uschek et al,,Anal,chem,,
47 (19751852), it is expressed by the following equation (3).

2ρ βe 2(5,4×1O10-Koe21'/2-(
3) However, ρ: the density of the sample (g/cm'1) 2: the atomic number of the sample A: the atomic weight of the sample, and the wavelength (cm) of incident X-rays, respectively.

The angle of incidence of the incident X-ray r is this total reflection critical angle β. If it is larger than , the incident X-ray r penetrates into the sample 10 and generates diffracted X-rays d and scattered X-rays S. Furthermore, when the incident angle β of the X-ray is smaller than the X-ray extraction angle a, that is, when 2θ=15°, the scattered X-rays S due to the unevenness of the surface of the sample 10 are rays into the detector, increasing the background intensity and reducing measurement accuracy. Such scattered X-rays S are generated by increasing the incident angle β of the X-rays from β1 to β2 as shown in FIGS. 8(a) and 8(b). It decreases by suppressing the However, as the angle of incidence β increases,
Since the line penetration depth 1p also increases, when measuring a thin film formed on the substrate 11 as the sample 10, the diffraction X 4?
1 d, and the method of setting the incident angle β to a large value is not suitable for structural analysis of the thin film sample 10.

Therefore, contrary to the above, the X-ray extraction angle α is set to O.

By setting the angle to be larger and as small as 5° or less, the incident angle β of the X-ray can be increased to a certain extent and the diffraction
If we take out the line d, the X-ray penetration depth is t.

is suppressed to a small value, and the scattering due to the unevenness of the surface of the sample 10, X! li! s is suppressed, and sample 1
A zero diffraction profile can be obtained with high sensitivity and accuracy.

! In the following, the X-ray diffraction method according to the present invention will be explained based on the drawings. Note that components having the same functions as those of the conventional example are given the same reference numerals.

FIG. 1 is a perspective view schematically showing an embodiment of an apparatus for carrying out the X-ray diffraction method according to the present invention.
indicates an X-ray source. Incident X generated from the X-ray source 12
The ray r passes through the Solar slit 13 and enters the surface of the sample 10, such as a thin film.
It sequentially passes through the second slit 16, and the monochromator 17
, passes through the third slit 18 and reaches the X-ray detector 19 .

In the above-described apparatus, the extraction angle α of the diffracted X-ray d is set in advance to a small angle of greater than 0° and less than 5°. Therefore, the penetration depth of the incident X-rays r into the sample 10 can be limited, and it is possible to obtain diffracted X-rays from the sample IO, such as a thin film, with a high diffraction intensity. In addition, since the X-ray extraction angle α is set to a small angle, even if the diffraction angle 2θ of the sample 10 is small, the incident angle β (β = 20−〇) of the X-rays to the substrate 11 can be set large. 10. Scattered X-rays S caused by surface irregularities can be suppressed.

There are two types of solar slits 13 on the incident side and the light receiving side.
．． 15 has the function of suppressing horizontal and vertical divergence to prevent a decrease in angular resolution, and monochromator 1
7 has the effect of removing fluorescent X-rays and lowering the background intensity.

Next, the results of measuring diffraction X##d using the method according to the above-described embodiment using Au formed on a glass substrate as sample 10 will be explained. Figures 2 to 4 are graphs showing the relationship between the X-ray extraction angle α and the detected X-ray intensity when the diffraction angle 2θ of sample 10 is 30°, 25°, and 20°, respectively. be. As is clear from FIGS. 2 to 4, the diffraction angle 2θ of the sample 10 becomes smaller (as it becomes smaller,
Furthermore, as the X-ray extraction angle α increases, the intensity I of the detected X-rays increases, indicating that the X-ray detector 19 contains scattered X-rays due to the unevenness of the surface of the sample 10. However, when the diffraction angle 2θ of sample 10 is 20°, xIJ
i! Even when the extraction angle is 3″′, the detected scattering
The intensity of the line ■ is about 5 cps. On the other hand, when the X-ray intensity I is measured using the conventional method when the incident angle β of the X-ray is 3°, as shown in FIG.
The intensity of scattered X-rays when the diffraction angle 2θ is 20° is 45
It also becomes cps.

From the above, by using the method according to the embodiment described above, the penetration depth of X-rays can be suppressed, and the diffraction X-rays from the sample 10 can be obtained with a large diffraction intensity. It can be seen that the scattered X-rays caused by this method can be significantly reduced. Therefore, the method according to the embodiment described above is effective in obtaining a 100-sample diffraction profile with high sensitivity and accuracy.

As detailed above, in the X-ray diffraction method according to the present invention, β: 2θ - α (2θ: diffraction angle of the sample, β: incident angle of the X-ray to the substrate) The X-ray extraction angle α is
Since it is set to be larger than Oo and 5° or less, even if the diffraction angle 2θ of the sample is 30° or less, the influence of scattered X-rays caused by unevenness on the sample surface can be reduced, and even if the sample has 100 people. Even with a relatively thin film, the diffraction profile of the sample can be obtained with high sensitivity and accuracy. Therefore, it becomes possible to perform structural analysis of the sample with high precision and accuracy.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing an embodiment of an apparatus for carrying out the X-ray diffraction method according to the present invention, and FIGS. °, 20°
A graph showing the relationship between the X-ray extraction angle a and the detected X-ray intensity I when Using equation (2), x#j! A graph showing the results of calculating the penetration depth, Figure 7 is a schematic diagram showing the situation when the sample surface is irradiated with incident xIa at the same angle as the critical angle Be of total reflection, Figure 8 is (a), (b) is a schematic diagram showing the relationship between the incident angle β of X-rays and scattered X-rays, Figure 9 is a schematic diagram to explain the conventional diffractometer method, and Figure 1O is the X-ray diffraction of a thin film. Fig. 11 is a schematic diagram showing the conventional method for measuring .
The figure shows X, ljj! when the incident angle β of X-rays is 3° using the conventional method. 3 is a graph showing the results of measuring the intensity I of . 10... Sample 11... Substrate r... Incident X-ray d... Diffraction Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 +5.0 20.0 25.0
30.0 turn angle 2e

Claims (1)

[Claims] (1) A sample formed on a substrate is irradiated with X-rays, and the diffracted X-rays are extracted to analyze the crystal structure of the sample.
An X-ray diffraction method characterized in that an X-ray extraction angle α expressed by β=2θ−α is set to be greater than 0° and less than 5°. However, 2θ: diffraction angle of the sample β: represents the incident angle of X-rays to the substrate, respectively.