JPH0933451A - Energy angle dispersion type total reflection X-ray analyzer - Google Patents

Abstract

(57) [Summary] [Structure] An X-ray absorption fine structure measuring apparatus for measuring energy dependence of X-ray reflectance, which is an energy angle dispersion type using a curved type polycrystal. It is possible to determine the X-ray incident angle for measuring the X-ray reflectance most efficiently for each sample and arbitrarily set the X-ray incident angle. Further, the film forming apparatus can be housed in the sample chamber, and measurement and analysis can be performed while forming a film, and the interface structure between the substrate and the thin film or the structure of the thin film can be continuously examined from the initial stage of film formation. [Effect] It is possible to measure a high S / N X-ray absorption fine structure in 1 to several seconds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray for analyzing the atomic level structure of a thin film constituting an electronic device such as a semiconductor element.
More particularly, the present invention relates to an X-ray absorption fine structure measuring apparatus suitable for analyzing the structure of the surface and interface of an amorphous thin film formed on a substrate.

[0002]

2. Description of the Related Art In the prior art, when the X-ray absorption fine spectrum of a thin film sample formed on a substrate is measured, for example, the measurement and analysis of X-ray absorption fine structure / XAFS, the Spectroscopy Society of Japan method series 26, pp. 138 to 146, a monochromatic crystal is used as a dispersive crystal to convert white X-rays into monochromatic light, which is then incident on a sample, and the energy dependence of the fluorescent X-ray yield from the sample is measured. It was done by the fluorescence method.

Further, for example, Applied Crystallography, Vol. 16, pages 220 to 232 (Journal of Applied Crysta
llography 16, 220-232, 1983)
Zackerley et al. "Energy dispersive spectrometer for rapid measurement of X-ray absorption spectra using synchrotron radiation".
(An Energy-Dispersive Spectrometer for the Rapid
Measurement of X-ray Absorption Spectra Using Sync
hrotron Radiation.), white X emitted from the X-ray source
X-rays are energy-dispersed by using a curved type polycrystal, X-rays with energy-angle dispersion are focused and transmitted to a sample, and the transmitted X-rays are measured by an X-ray film or a position-sensitive detector. The line absorption fine spectrum was measured.

[0004]

Fluorescent X for measuring the energy dependence of the fluorescent X-ray yield of a thin film sample formed on a substrate by monochromatic white X-rays using a monochrome crystal and entering the sample. High S when using a line absorption fine structure measuring device
In order to measure / N, it is necessary to integrate the weak fluorescent X-rays from the thin film, and the measurement time per energy is several to several tens of seconds. Therefore, considering the number of scanning points of the monochrome crystal and the measurement time, the measurement time per sample needs to be at least 1 to 2 hours.

If an energy dispersive X-ray absorption fine structure measuring device is used, it is possible to measure in 1 to several seconds per sample. However, since the X-rays are transmitted through the sample for measurement, a film is formed on the substrate. It was not applicable to the measurement of thin film samples.

It is an object of the present invention to enable high-speed measurement of the X-ray absorption fine structure of a thin film sample on a substrate, even though it is an energy angle dispersion type X-ray absorption fine structure measuring device using a curved polychrome crystal. An object is to provide an X-ray analyzer.

[0007]

In order to achieve the above object, the energy dispersive X-ray absorption fine structure measuring apparatus of this embodiment utilizes the total reflection phenomenon of X-rays to determine the energy dependence of its reflectance. It is an X-ray absorption fine structure measuring device for measurement.

Further, a means for automatically determining the X-ray incident angle is provided so that the analysis accuracy is maximized according to the type of the measurement sample.

Further, means for inclining the sample stage with respect to the X-ray beam axis, means for rotationally moving about the X-ray beam axis, and means for vertically moving are provided, and the incident angle of X-rays on the sample is arbitrarily set. Provide a mechanism to set.

Further, the apparatus is equipped with a film forming apparatus for accommodating the sample table in a container having a film forming means and forming a thin film sample as needed.

[0011]

Since the energy angle dispersion type using the curved type polycrystal is used as the X-ray absorption fine structure measuring apparatus for measuring the energy dependence of the X-ray reflectance, even a thin film sample formed on the substrate can be quickly processed. It is possible to perform various measurements and to determine structural parameters such as interatomic distances with the same high precision as the fluorescence method.

Further, since the film forming apparatus is housed in the sample chamber, measurement and structural analysis can be performed during film formation, and the interface structure between the substrate and the thin film or the structure of the thin film is continuously examined from the initial stage of film formation. can do.

[0013]

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a side view showing an outline of an energy angle dispersion type total reflection X-ray analysis apparatus as an embodiment of the apparatus of the present invention. White X-rays 12 generated from the X-ray source 11 are shaped by a slit 13, high-energy X-rays unnecessary for measurement are removed by a total reflection mirror 14, and the curved polychromatic crystal 1
5 is incident. The X-rays 16 whose energy angle is dispersed by the curved polychromatic crystal pass through the slits 17 for removing scattered X-rays, and are focused on the sample 18 to be incident on the sample fixed on the sample table 19. The sample stage 19 can be moved up and down and rotated about the incident X-ray beam axis, and can be tilted to change the incident angle with respect to the incident X-ray. Energy angle reflected X-rays 110 from the sample are scattered X-ray removal slits 11.
After passing 1, the X-ray intensity is measured by a one-dimensional detector 112 such as a photodiode array. If the entrance window of the detector 112 is set large enough,
The X-ray 110 reflected by the sample 18 can be measured without moving the detector 112. The sample chamber 113 and the detector 112 can be moved in the horizontal direction or the vertical direction of the X-ray beam on the apparatus mount according to the measurement conditions.

Although not shown in the drawing, a film forming means such as sputtering or CVD is provided inside the sample chamber to enable measurement while forming a film or measurement while scraping the sample surface.

FIG. 2 is a diagram showing the principle of the energy angle dispersion type X-ray absorption fine structure measuring apparatus using the curved type polycrystal of the apparatus of the present invention. In order to select only the photons having a specific wavelength λ (nm) or energy −E (eV) from the incident X-rays 21 having a wide energy component to make them monochromatic,
The diffraction angle (θ) of the dispersive crystal is set according to Formula 1 or Formula 2 known as Bragg's law. Here, d is the surface spacing (nm) of the diffraction surface of the dispersive crystal.

[0017]

[Equation 1]

[0018]

[Equation 2]

When the dispersive crystal is a curved polycrystal as in this embodiment, the diffraction angle (θ) 22 differs depending on the position of the incident X-ray 21 incident on the dispersive crystal. When X-rays having different diffraction angles or different energies are converged on the measurement sample, the X-rays are dispersed again at an arbitrary angle and reach the detector 23. Therefore, by measuring the X-ray intensity of each channel of the detector using the one-dimensional detector, the spectrum of the X-ray absorption fine structure in a wide energy range can be measured at one time. Equation 3 shows the relationship between the diffraction angle (θ) of the curved polycrystal and the channel (n) of the detector.

[0020]

(Equation 3)

Where θB is the diffraction angle at the central position of the curved polycrystal, L is the horizontal width of the light receiving portion of the detector, l is the distance from the focus on the sample to the detector, and N is the total channel of the detector. Is a number. Even without using a one-dimensional detector here, for example, a slit is provided in front of the light-receiving surface of the scintillation counter detector, and the slit is scanned at a constant speed in front of the light-receiving surface to perform pseudo one-dimensional detection. You may use a container.

Further, it is possible to replace the spectral polycrystal according to the target energy band. In this embodiment, Si (31
1) Although a curved polycrystal is used, a curved polycrystal such as Si (111) or a multilayer reflective film may be used depending on the intended energy band.

The energy resolution, which is directly related to the quality of the spectrum of the X-ray absorption fine structure, has the divergence angle of the X-ray as a light source (Equation 4), the spatial resolution of the detector (Equation 5), and each polycrystal. It depends on the intrinsic angular resolution (Equation 6).

[0024]

(Equation 4)

[0025]

(Equation 5)

[0026]

(Equation 6)

[0027]

(Equation 7)

The total energy resolution is determined according to equation (7). Where p is the distance between the X-ray source and the crystal, q is the distance between the crystal and the focus on the sample, d is the distance between the focus on the sample and the detector, R is the radius of curvature of the curved crystal, and ΔS is the X-ray. Indicates the width of the beam.

FIG. 3 shows changes in energy resolution under various measurement conditions.

The principle of the absorption fine structure obtained by measuring the X-ray reflectance will be briefly described below.

In the absorption fine structure based on the reflectance of X-rays, vibration occurs due to anomalous dispersion of X-rays on the higher energy side than the absorption edge of atoms contained in the sample surface. This vibrating structure contains information corresponding to the X-ray absorption fine structure.

Here, the complex refractive index n of the sample is given by
It can be expressed by Equation 10. Where δ is the real part of the refractive index,
β is the imaginary part of the refractive index, μ is the linear absorption coefficient, and λ is the wavelength.

[0033]

(Equation 8)

[0034]

[Equation 9]

[0035]

(Equation 10)

At this time, the reflectance (R) is given by the formula 11 from the Fresnel's formula.

Here, assuming that the incident angle is φ, the critical angle for total reflection is φc, and X << 1 with X = φ / φc and Y = B / δ, Equation 11 is approximately represented as Equation 12. be able to.

[0038]

[Equation 11]

[0039]

(Equation 12)

When β is calculated based on the equation 12, the equation 13 is obtained.
It is represented as

[0041]

(Equation 13)

That is, R is a function of β and δ, and δ at this time changes monotonically with respect to the wavelength or energy of incident light. That is, assuming that it does not contribute to the vibration structure, the R vibration structure is given by the β vibration structure.

Therefore, from the relationship between the equations 10 and 13, the equation 1
It was decided to determine the X-ray absorption fine structure from the vibrating structure of μ represented by the formula (4).

[0044]

[Equation 14]

In this way, the vibration of the X-ray absorption fine structure can be extracted from the actually measured reflectance R by a method similar to the transmission method or the fluorescence method, and the structural parameter such as the interatomic distance can be obtained.

Next, the setting of the X-ray incident angle according to this embodiment was performed by the following procedure.

(1) The X-ray incident angle to the sample is 0.1 to
The X-ray absorption edge energy of the measurement sample is determined by setting it to 0.3 degree.

(2) In order to measure the dependency of the reflectance on the X-ray incident angle on the higher energy side (up to 100 eV) than the X-ray absorption edge energy, the sample stage is fixed at, for example, 0 degree to 0.01 degree step. The reflectance curve is obtained by scanning up to about 1 degree.

(3) From the obtained reflectance curve, the angle at which the reflectance is 0.5 is the critical angle for total reflection.

(4) The sample stage is set with the total reflection angle being the angle at which the reflectance is 0.6 to 0.8 at an angle smaller than the total reflection critical angle.

The above X-ray incident angle setting is automatically set by the computer provided in the measuring apparatus of this embodiment. This X-ray incident angle setting may be set once before the measurement, and does not need to be reset unless the sample is changed.

Next, an example of the spectrum of the X-ray absorption fine structure of the Pb (Zr, Ti) O ₃ thin film sample formed on the substrate, which was measured by using this example, is shown in FIG. The measurement energy range is 12.98 to 13.44 keV, and the measurement time is
1 second. Figure 5 shows the radial distribution function obtained from the X-ray absorption fine structure spectrum. The peaks at 0.25 nm, 0.28 nm, and 0.32 nm coincide with the Pb-O distance of Pb (Zr, Ti) O ₃ . Figure 6
Indicates the Pb-O distance, which is the distance between the first adjacent atoms of Pb obtained by numerical analysis of the radial distribution function. Moreover, the value of the fluorescence method measured over 2 hours is also shown at the same time.

From the above results, when the X-ray absorption fine structure was measured using the energy angle dispersion type total reflection X-ray analysis apparatus according to this example, the fluorescence method was used in the measurement time of several hundred to several thousandths. It was found that equivalent analysis results were obtained.

[0054]

EFFECT OF THE INVENTION An energy angle dispersion type using a curved type polycrystal, which measures the energy dependence of X-ray reflectance X
Since it is a linear absorption fine structure measuring device, even a thin film sample formed on a substrate can be measured at a measurement time of several hundreds to several thousandths of that of the fluorescence method, and the highly accurate interatomic distance, etc. of the same level as the fluorescence method. The structural parameters of can be determined.

Further, since the film forming apparatus is housed in the sample chamber, measurement and structural analysis can be performed during film formation, and the interface structure between the substrate and the thin film or the structure of the thin film is continuously examined from the initial stage of film formation. can do.

[Brief description of drawings]

FIG. 1 is a side view showing an outline of an energy angle dispersion type total reflection X-ray analysis apparatus which is an embodiment of the present invention.

FIG. 2 is an explanatory view showing the principle of an energy angle dispersion type X-ray absorption fine structure measuring apparatus using a curved polychrome crystal which is an example of the present invention.

FIG. 3 is an explanatory diagram showing changes in energy resolution under various measurement conditions that are examples of the present invention.

FIG. 4 is a Pb film formed on a substrate according to an embodiment of the present invention.
(Zr, Ti) characteristic diagram of the spectrum of the X-ray absorption fine structure of the O ₃ thin film sample.

FIG. 5 is a Pb film formed on a substrate according to an embodiment of the present invention.
FIG. 4 is a characteristic diagram showing a radial distribution function obtained from an X-ray absorption fine structure spectrum of a (Zr, Ti) O ₃ thin film sample.

FIG. 6 is a Pb film formed on a substrate which is an example of the present invention.
(Zr, Ti) O ₃ explanatory view showing a Pb-O distance is first closest interatomic distance of Pb with a radial distribution function and numerical analysis of the thin film sample.

[Explanation of symbols]

 11 ... X-ray source, 12 ... White X-ray, 13 ... Slit, 14 ... Total reflection mirror, 15 ... Curved polychromatic crystal, 16 ... Energy angle dispersion X-ray, 17 ... Slit, 18 ... Sample, 19 ... Sample stand, 110 ... Reflected X-ray, 111 ... Slit, 112 ... One-dimensional detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazufumi Suenaga 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ltd.

Claims (4)

[Claims] 1. X-rays from an X-ray source, which are incident on a curved polychromatic crystal, are energy-angle-dispersed, are focused on a sample, and are energy-angle-dispersed. In an energy angle dispersion type X-ray absorption fine structure measuring apparatus for measuring with an X-ray detector, incident X-rays on the sample are made incident at a predetermined angle, and reflected X-rays from the measurement sample on the sample stage are measured. By doing so, the energy angle dispersion type total reflection X-ray analysis apparatus is characterized in that the X-ray absorption fine structure is measured by the energy dependence of the X-ray reflectance. 2. The energy-angle-dispersed total reflection X according to claim 1, wherein means for automatically determining an X-ray incident angle is provided so that analysis accuracy is maximized according to the type of the measurement sample. Line analyzer. 3. An X-ray to a sample according to claim 1, further comprising: a means for inclining the sample stage with respect to the X-ray beam axis, a means for rotationally moving about the X-ray beam axis, and a means for vertically moving. Energy dispersion type total reflection X-ray analysis apparatus provided with a mechanism for arbitrarily setting the incident angle of. 4. The energy-angle-dispersion total reflection X-ray analysis apparatus according to claim 1, further comprising a film forming device for accommodating the sample stage in a container having a film forming means, and forming a thin film sample as needed. .