JPH01296148A - Total reflection type expanded x-ray absorption fine structure measuring apparatus - Google Patents

Abstract

PURPOSE:To enable measurement of a thin film or even a highly concn. sample on a substrate, by monitoring a dose of X rays incident into parallel monochromatic fine X-ray luminous fluxes after a shaping to detect totally reflected X rays from the surface of the sample with a set angle of incidence. CONSTITUTION:X rays radiated from an X-ray source 1 are black reflected with a monochrometer 2 wherein a specified crystal face is inclined by a specified angle theta to an X-ray radiation axis to make a monochromatic X-ray luminous flux. The X rays are further turned to a fine X-ray luminous flux with a higher monochromatic property and a greater parallelism with the passage through a second slit S2. The luminous flux shaped by these X-ray shaping means is monitored 7 in incident X-ray dose and incident into a sample 4 whose angle of incidence is set below a total reflection critical angle on the short wavelength side in a measuring wavelength range. The totally reflected X rays from the sample 4 pass through a third slit S3 to detect intensity thereof with an X-ray detector 9. Thus, an absorption of the totally reflected X rays is judged from the results and the incident X-ray dose.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a total internal reflection type extended X-ray absorption fine structure measuring device for analyzing the surface local structure of a substance.

Conventional technology In general, the extended X
Linear absorption fine structure (Extended X-ray Ab
s.

rption fine structure (hereinafter abbreviated as "EXAFS") is important. this is,
By injecting monochromatic X-rays into a sample and continuously changing the wavelength, we measure the absorption edge of the atom of interest, for example, the fine structure spectrum of X-ray absorption that appears on the high energy side from the absorption edge. This is a structural analysis method in which the type, number, coordination distance, etc. of the nearest neighbor and second neighbor atoms around the atom of interest are determined from the Fourier transform of the vibrational spectrum.

Conventionally, two methods have been used: a transmission type EXAFS method that measures xl transmitted through a sample, and a total reflection type fluorescence EX method that completely reflects incident X-rays on the sample surface and measures the fluorescent X-rays emitted at this time.
This method is limited to either the AFS method or the AFS method. However, in the case of the former transmission type EXAFS, it is not possible to measure EXAFS of a thin film on a substrate because it is affected by the substrate. On the other hand, the latter total reflection fluorescence EXAFS method
For example, it is known from Japanese Patent Application Laid-Open No. 62-214335, and although it is possible to measure thin films on a substrate,
At high concentrations, the fluorescent X-ray intensity is no longer proportional to the absorption coefficient, so careful attention is required when measuring at high concentrations.

Purpose The present invention was made in view of the above points, and it is an object of the present invention to provide a total internal reflection type extended X-ray absorption fine structure measuring device that can easily measure not only thin films on a substrate but also highly concentrated samples. With the goal.

Structure In order to achieve the above object, the present invention provides an X# that emits X-rays.
An I source is installed, and the X-rays from this X-ray source are converted into monochromatic parallel fine X-rays.
An X-ray shaping means for shaping the beam into a linear beam is provided, a monitoring means is provided for monitoring the incident X-ray dose after shaping by the X-ray shaping means, and the angle of incidence of the incident X-ray on the sample to be measured is determined on the short wavelength side of the measurement wavelength range. X&! is set below the critical angle of X&! A detector is installed,
The present invention is characterized in that a removal member is provided that faces the sample and removes the influence of direct X-rays on the X-ray detector.

Hereinafter, one embodiment of the present invention will be described based on the drawings. First, white X-rays emitted from the X-ray source 1 pass through the first slit S1, and then set a predetermined crystal plane in a predetermined direction (that is, tilted at an angle θ with respect to the X-ray emission axis). The monochrome X is reflected by the monochromator 2
It becomes a line. Note that the monochromator 2 uses a single or double monochromator made of a complete single crystal such as a Si wafer.

The monochromatic X-rays further pass through the second slit S2 to become a fine X-ray beam with good monochromaticity and parallelism. That is, the monochromator 2 and the second slit S2 constitute the X-ray shaping means 3.

Then, the fine X-ray beam shaped by the X-ray shaping means 3 is incident on the surface of the sample 4 to be measured, here the surface of the thin film 6 formed on the sample substrate S. At this time, the incident angle of the incident X-ray with respect to the surface of the thin film 6 is on the short wavelength side of the measurement wavelength range (measurement energy range) (usually an energy position of about IKeV from the absorption edge of interest to the high energy side)
The sample 4 is arranged so that the total reflection critical angle θC is less than or equal to the total reflection critical angle θC.

Then, the sample 4 passes through the second slit S2.
Before the incident X-rays are incident on the surface, the amount of incident xl I. is monitored by passing it through the monitoring means 7. For example, the monitoring means may be configured to measure the intensity of the incident X7 rays by filling a chamber made of stainless steel or the like with a gas such as He and applying a high voltage. That is, in the case of a monitoring method using an ion chamber with an incident X-ray dose of 1°, about 10% of the incident intensity is used for detection.

Additionally, a knife 8 is installed at the point of incidence of the X-rays on the surface of the sample 4 as a removal member for directly removing the influence of the X-rays.
is provided perpendicularly to the surface of the sample 4. The knife 8 is made of a material with good X-ray absorption properties, such as an alloy of Pb and MO. Therefore, the X-rays incident on the surface of the sample 4 pass through the gap between the surface of the thin film 6 and the tip of the knife 8, are totally reflected on the surface of the thin film 6, pass through the third slit S3, and are detected by the X-ray detector 9. be measured. Note that a beam stopper 10 that directly cuts X-rays is also provided.

The X-ray detector 9 is, for example, an energy dispersive type semiconductor detector, and detects the intensity 1 of the total reflection of the X-rays from the thin film 6. Here, since the incident X-ray dose 10 is monitored by the monitor means 3, by detecting the intensity of the totally reflected X-rays with the X-ray detector 9, the amount of totally reflected X-rays absorbed can be determined.

In such a configuration, the total reflection critical angle θC is as small as -S by several tens of minutes (for example, when the wavelength of the incident X-ray is λ=1.
If there are 5405 people and sample 4 is Au, the critical angle 0c = 34
'), since the X-rays are incident on the surface of the sample 4 at an incident angle smaller than the critical angle θC, the X-rays are totally reflected on the surface. Therefore, since the X-rays are incident at an incident angle smaller than the small critical angle θC, the penetration depth of the X-rays into the thin film 6 is as small as several tens of people, making it possible to perform measurements sensitive to the sample surface. At this time, since the critical angle θC is small as mentioned above,
When the X-ray detector 9 detects the total reflection XNA from the thin film 6, it is likely to be affected by the direct X-rays, resulting in a poor S/N ratio. We are trying to minimize the impact of
This results in a good S/N ratio. Furthermore, the conventional total reflection type E
The amount of absorption of directly incident light is measured by detecting total internal reflection X-rays rather than secondary X-rays (fluorescent X-rays) as in the XAFS method, making it possible to measure even in the case of highly concentrated thin film samples. It is possible.

Next, taking the case where sample 4 is selenium Se as an example, EXA
A method of calculating the set angle when measuring FS will be explained.

First, if the macroscopic permittivity of the thin film is 1, then i(ω)=
It is expressed as 1-4 xe"N/mω".

However, N (cm-') is the electron density, e (cgs) is the charge production, e=4.803×10-th, and mug) is the electron mass, m=9. ll0XIO”””.

Here, the refractive index n(ω) of the substance for X-rays is n(ω
)=J17Ty■, so n(ω) is 1, and when X-rays enter a substance from a vacuum at a critical angle of θC (radian) or less, total reflection occurs. Here, if we set g(ω) = 1-26, δ = 2 yt e"FJ/mω" ((1, so the refractive index of the material for X-rays is n(ω) = J(1-
2δ] #1−δ.

On the other hand, the critical angle θC is 1cosθ according to Snell's law.
It is determined from c=ncos○. The critical angle of total reflection is θ
c well O, so by expanding COSθC, e cmJ28= (eλ/c)V/N bow [1= (
e h/E) JpA, z/rcmM However, blank constant h=6,626X10-27, Avogadro's number A0=6.
022X102', and for trigonal Se, the density, ρ
[g−釧−”)=4°808, number of electrons Z=34, and mass M=78.96.

Here, the absorption edge wavelength λab of selenium Se is 0°97
From 98-” [cn], Eab= 12.653 (Ke
V). EXAFS measurement range is ±I for Eab.
A range above and below about KeV is sufficient. Therefore, the high energy end of this measurement region is 13,653 (KeV).

Also, by calculating the above formula, the critical angle 0c=3,036X1
We get 0-'(radian)=10.4'.

Therefore, for incident X-rays that enter the Se thin film surface at an incident angle less than this critical angle θC, the energy thereof is 13.
EXAFS measurements can be performed in the region below 653 (KeV). In this way, the local structure of the Se thin film 6 deposited on the substrate 5 can be evaluated.

Effects As described above, the present invention is configured to measure the absorption of X-rays that are totally reflected on the sample surface, so that measurement that is sensitive to the sample surface is possible, and thin films on the substrate can be measured.
Since the removal member directly removes the effects of X-rays, S
It becomes possible to measure with a good /N ratio, and furthermore, by detecting totally reflected X-rays instead of secondary X-rays, even highly concentrated samples can be measured.

[Brief explanation of the drawing]

The drawing is a schematic front view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...X-ray source, 3...X-ray shaping means, 4...sample, 8...removal member, 9...X-ray detector 1 (bi side J

Claims (1)

[Claims] an X-ray source that emits X-rays; an X-ray shaping means that shapes the X-rays into a monochromatic parallel fine X-ray beam; a monitor means that monitors the amount of incident X-rays after shaping; a sample whose incident angle is set to be less than or equal to the critical angle on the short wavelength side of the measurement wavelength range; an X-ray detector that detects total internal reflection from the surface of the sample; and an X-ray detector that faces the sample and detects the X-rays. 1. A total internal reflection type extended X-ray absorption fine structure measurement device, comprising a removal member that removes the influence of direct X-rays on the instrument.