JPH0627052A - Sample holder for measurement of x-ray reflectance and x-ray reflectance measuring method - Google Patents

Abstract

PURPOSE:To allow accurate measurement of original point angle of 0 deg. when projecting X-ray to a sample and measuring reflectance thereof. CONSTITUTION:The sample holder 11 for measurement of X-ray reflectance is located on the same plane as a sample 14 to be measured at a part of the optical path of incident X-ray and a crystalline thin film part 15, having known spacing of lattice plane, is provided thereon. When X-ray is projected onto the sample 14 in order to measure the reflectance thereof, X-ray is also projected onto the crystalline thin film part 15 in order to measure a diffraction peak thereof thus allowing correction of reflectance data based on the diffraction peak value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray reflectance measuring sample holder used for quantitative analysis of a material surface and the like, and an X-ray reflectance measuring method using the same.

[0002]

2. Description of the Related Art Conventionally, as this type of reflectance measuring method,
A low incidence angle X-ray reflectance measurement method is generally used, and a measurement sample holder 1 as shown in FIG. 2 or 3 is used.
In the case of FIG. 2, a rectangular opening 3 is formed in the X-ray irradiation portion of a holder substrate (made of an aluminum plate, a glass plate, etc.) 2 having a size of L = 30 mm and H = 40 mm, and the rectangular opening 3 is made of powder. The sample to be measured 4 such as the above is filled, and the X-ray irradiator irradiates the X-ray with rotating the sample holder 1 for measurement around the axis 5. In FIG. 3, a rectangular recess 6 is formed in place of the rectangular opening 3 to fill the sample 4 to be measured.

Considering a low incidence angle X-ray reflectance measuring method using such a sample holder 1 for measurement, as shown in FIG. 4, an X-ray 7 is angle α <3 with respect to the surface of the sample 4 to be measured. °
When making the incidence at the following low incident angles and measuring the reflectance,
It is necessary to know the angle of the origin (= 0 °) accurately.

[0004]

Here, conventionally, when the X-ray 7 and the surface of the sample 4 to be measured are parallel (= 0 °), the count number of the detector 8 becomes maximum. So
Although this is the origin, the incident X-ray 7 also has a width and has a distribution characteristic as shown in FIG. 5, so the obtained origin position is not always accurate.

This point will be described in more detail.
First, the principle of the low incidence angle X-ray reflectance measurement method will be described. X
The line 7 has a short wavelength (several 10 Å to 0.1 Å), and the refractive index of the substance is almost equal to 1. When the X-ray 7 is incident on the surface of the solid body at a grazing angle, total reflection occurs. The critical angle θc is usually about 10 to 30 ′, and becomes larger as the wavelength of the X-ray 7 becomes longer. By utilizing this total reflection, the curved mirror is used for collecting light. Also, X-ray 7
Shows an interference phenomenon like light, and when the phases are aligned, the waves strengthen each other. By the way, as shown in FIG. 6, when the X-ray 7 is incident on the surface of the sample to be measured 4 at a grazing incidence angle α, the wave reflected on the surface of the sample to be measured 4 and the wave reflected on the surface of the holder substrate 2 are separated. Are aligned at a certain angle α ₁ and have a relationship as shown in FIG. This is 2
It occurs when the optical path difference of two X-rays is equal to an integer multiple of the incident X-ray wavelength. If the film thickness of the sample 4 to be measured is not more than 1000 Å, the X-ray 7 does not reach the holder substrate 2 and this phenomenon does not occur. The sample 4 to be measured may be crystalline or amorphous, and the point is that it should be uniform.

By the way, the substance of the sample 4 to be measured is 1000
If the thickness is made thinner than Å and the multi-layer structure is provided, the above interference effect is increased. However, the layers must be mirror-finished. However, according to the current manufacturing technology, it is possible to provide several thin film layers uniformly. For example, a LB film or a semiconductor such as GaAs provided by MBE (molecular beam epitaxy) can be used. When the incident angle α is α ₁ , the reflected X-rays are monochromatic (spectralized) according to the above-mentioned principle and have the same phase.

Such a measurement is generally performed by α <3 °,
In particular, it becomes a measurement of low angle incidence where α <2 °. Here, the film thickness is obtained by the period of vibration, the surface roughness is obtained from the manner of attenuation of strength, and the density of the film is obtained from the critical angle. Such contents are reported, for example, in the document “LG Parratt: Phys. Rev., 95.p359” and the document “Y. Yoneda: Phys. Rev., 131.p2010”.

By the way, as described above, 0 ° is when the incident X-ray 7 becomes parallel to the surface of the sample 4 to be measured, and at this time, the detection intensity by the detector 8 becomes maximum. However, in reality, the surface of the sample 4 to be measured may not be a perfect plane but may be curved.
The line 7 also has a width and a distribution. Therefore, as shown in FIG. 8, when the sample 4 to be measured is rotated about the axis 5, the relationship between the center of rotation and the incident X-ray 7 is not always constant if strictly considered. Every time you replace the, there is a gap.

Therefore, in the ideal case, as shown in FIG. 9, a peak occurs at a position of 0 °, but in reality, the intensity distribution as shown in FIG. And the profile around the peak fluctuates. In particular,
Even in the case of a material whose critical angle is known, such as Si, there may be cases where the zero points obtained from this critical angle do not match. So, in general, when reading data,
Since the angle from the 0 point is read, if the 0 point is originally deviated, the data will be erroneously read.

By the way, there are many literatures and reports on the total reflection X-ray measurement method, and in particular, in recent years, an apparatus using the total reflection X-ray fluorescence analysis method for quantifying impurities on the surface of a substance is commercially available. In addition, the reflectance measurement at a low incident angle for investigating the interface state of the multilayer film has become popular, but the above problems are not taken into consideration.

[0011]

According to a first aspect of the present invention, the lattice plane spacing has a known value by being located on the same plane as the sample surface to be measured, which is a part of the incident X-ray optical path. A crystalline thin film portion is provided, and in the invention according to claim 2, when measuring the reflectance of the sample to be measured by making X-rays incident on the sample holder for measuring X-ray reflectance according to claim 1, X-rays were also made incident on the crystalline thin film portion to measure its diffraction peak, and the reflectance data was corrected based on this diffraction peak value.

[0012]

In the present invention, the X-ray reflectance measuring sample holder itself is provided with a crystalline thin film portion having a known lattice constant, that is, a lattice plane interval, by utilizing a part of the holder. The reflectance data can be corrected by referring to the measured value of the diffraction peak of the crystalline thin film portion for each measurement of the sample portion to be measured, and accurate measurement is possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG. In this embodiment, the holder substrate 1 of the measurement sample holder 11 is used.
A crystalline thin film portion 15 having a known lattice constant, here, a lattice plane interval d, is provided in a part of the filled portion of the measured sample 14 by the rectangular concave portion (or rectangular opening) 13 formed in 2.
The peak value of the crystalline thin film portion 15 can be referred to and corrected and analyzed every time the measurement sample 14 surface is measured. The sample holder 11 for measurement is rotated about the axis 16 at the time of measurement. Here, the crystalline thin film portion 15
Is located in a part of the optical path of the incident X-ray and is set to be flush with the sample 14 to be measured.

For example, α type stearic acid has a lattice spacing d of d = 39.40Å, and when CuKα rays (wavelength λ = 1.54Å) when Cu is used as the X-ray source,
From 2d · sin θ = nλ, a diffraction peak appears at an angle θ = 1.12 °. Thus, in addition to the so-called fatty acids, organic / inorganic substances may be used. When molybdenum is used as the X-ray source, d> 6.8Å (6 at 2θ,
θ is within 3 °), and when Cu is used, d> 1
Any material may be used as long as it has a value of the lattice spacing d of 4.7 ° Å or more (6 ° for 2θ and within 3 ° for θ). The crystalline thin film portion 15 may be in the form of powder or thin film, and may be extremely thinly provided on the measured sample 14. Further, since it is only necessary to know the peak position of the diffraction peak, a minute amount may be sufficient.

A more specific embodiment will be described. First, a small amount of α-type stearic acid (purity 99.999%) was dissolved (about 1% concentration) in the rectangular concave portion 13 portion formed on the holder substrate 12 made of a Si wafer, and hatched in FIG. Part of the liquid droplets was added to the portion indicated by, and this was drawn out and dried to form the crystalline thin film portion 15. At the same time, a sample (comparative sample) of only the Si wafer without the stearic acid was prepared. Then, according to the low incidence angle X-ray reflectance measurement method described above, the X-rays were made incident on the both samples at a low incidence angle to perform the measurement. Here, as the X-ray apparatus, an improved one based on RU-300 manufactured by Rigaku Co., Ltd. was used. Cu for the target
The sample 14 to be measured was irradiated with CuKα rays dispersed by Si (111). Therefore, the incident angle is 0
Change in the range of 2 ° to 2 ° (voltage × current = 40 kV × 6
When the relationship between 0 mA) and the reflectance was measured, a diffraction peak was observed at a position where the incident angle was 1.1 °.
When this angle is set to a known theoretical value of 1.12 ° and the critical angle of the Si wafer is calculated by correction calculation, it becomes 0.22 °, which is in agreement with the true value shown in the literature.

By the way, in the case of the comparative sample using only the Si wafer without the stearic acid, -0.5 ° to 2 °
The angle of incidence was changed within the range of ## EQU1 ## and the angle at which the maximum peak value was given was 0 °. The critical angle of the Si wafer was determined to be 0.15 °, which was a considerable deviation from the true critical angle. It has become.

The method of the present invention can be applied not only for measuring low incidence angle X-ray reflectance but also for more general high incidence angle X-ray diffraction.

[0018]

According to the present invention, the X-ray reflectance measurement sample holder itself is provided with a crystalline thin film portion having a known lattice constant, that is, a lattice plane interval, by utilizing a part thereof. Since the correction data was obtained by measuring the diffraction peak of this crystalline thin film portion at the time of measurement, the reflectance was measured by referring to the measured value of the diffraction peak of this crystalline thin film portion for each measurement of the measured sample portion. It becomes possible to correct the data, which enables accurate measurement.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of the present invention.

2A and 2B show a configuration of a conventional sample holder, in which FIG. 2A is a schematic perspective view and FIG. 2B is a longitudinal side view thereof.

FIG. 3 shows a configuration of a different conventional sample holder, (a)
Is a schematic perspective view, and (b) is a longitudinal side view thereof.

FIG. 4 is an explanatory diagram showing a low incidence angle X-ray reflectance measurement method.

FIG. 5 is an intensity distribution characteristic diagram of the incident X-ray.

FIG. 6 is an explanatory diagram showing the principle of a low incidence angle X-ray reflectance measurement method.

FIG. 7 is an X-ray incident angle-reflection intensity characteristic diagram.

FIG. 8 is an explanatory diagram showing that an incident X-ray has a width.

FIG. 9 is an X-ray incident angle-X-ray intensity characteristic diagram.

[Explanation of symbols]

 11 sample holder for measurement 14 sample to be measured 15 crystalline thin film part

Claims (2)

[Claims] 1. A crystalline thin film portion having a known lattice plane interval is provided on a part of the incident X-ray optical path on the same plane as the sample surface to be measured. Sample holder for X-ray reflectance measurement. 2. When the X-ray reflectance is measured on the sample holder for measuring X-ray reflectance according to claim 1, the X-ray is also incident on the crystalline thin film portion. The X-ray reflectance measuring method is characterized in that the diffraction peak is measured by means of the measurement, and the reflectance data is corrected based on the diffraction peak value.