JPH05196583A - Total reflection x-ray analyzer - Google Patents

Abstract

PURPOSE:To set forth X-ray incident position and incident angle thereof with very good repeatability and to enable highly accurate measurement of X-ray scattering, X-ray diffraction, EXAFS and phosphorescent X-ray at multi-layer- thin-film-interface.surface, in a total reflection X-ray analyzer. CONSTITUTION:X-ray is monochromized by a 14 and by an X-ray collecting mirror 15. Subsequently, the X-ray 1 of which harmonics is removed by an X-ray reflecting mirror 16, is made to come into a sample 4 by very small incident angle less than total reflection critical angle. A sample table 4 has an elevating mechanism and a rotating mechanism. While monitoring a scattering X-ray intensity detector 11, sample position is set forth to have the optimum total reflection condition, and therewith reflecting X-ray and phosphorescent X-ray are measured.

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 evaluating a material using X-rays as a probe, and particularly to X-ray scattering, X-ray scattering at the interface / surface of a multilayer thin film used for semiconductor elements and the like.
The present invention relates to a total reflection X-ray analysis apparatus suitable for analyzing the atomic / molecular arrangement of a material by measuring line diffraction, EXAFS, fluorescent X-rays, etc., or performing ultratrace analysis of the surface.

[0002]

2. Description of the Related Art In the prior art, for example, Physical Review B Vol. 38, pages 1019 to 1026 (Physi
cal Review B38, 1019-1026.
1988). M. Heald et al., "Study of extended X-ray absorption edge fine structure and reflectance of interfaces by grazing incidence method" (Glanching-angle ex)
tended x-ray-absorption f
ine structure and reflect
ivity studies of interfac
As described in “Ial regions”, the energy of incident X-rays is continuously scanned by fixing the incident angle to an angle smaller than the critical angle of total reflection that causes X-rays incident on the sample to cause total reflection phenomenon. However, the reflectance is measured by an incident X-ray intensity detector and a reflected X-ray intensity detector, and the fluorescence yield is measured by a fluorescent X-ray detector.

[0003]

The critical angle for total reflection when X-rays are incident on the sample surface is, for example, about 0.2 ° to 0.6 ° for X-rays having a wavelength of 0.15 nm. When X-ray spectroscopic measurement such as reflectance and fluorescence yield is performed by using the total reflection phenomenon of X-rays, it is necessary to make X-rays incident on the surface of the sample smaller than the critical angle for total reflection. At this time, in order to perform a highly accurate measurement, it is necessary that all the X-ray beams are incident on the sample surface and not on the sample side surface and that the incident angle is set with good reproducibility.

However, in the above-mentioned prior art, since the position of the X-ray beam and the position of the sample surface on the sample stage and the adjustment of the X-ray beam and the sample rotation axis are not taken into consideration, the thickness and size of each sample to be actually measured. If the shapes are different, it is difficult to set the position with good reproducibility.

An object of the present invention is to set an X-ray incident position and an incident angle with good reproducibility in a total reflection X-ray analyzer to perform highly accurate measurement.

[0006]

In order to achieve the above object, in the present invention, a scattered X-ray intensity detector for measuring the X-ray intensity scattered from the sample, and an incident angle of the incident X-ray beam to the sample. And a sample moving mechanism for moving the incident position of the X-ray beam on the sample in a direction parallel to the X-ray beam, and the incident angle of the incident X-ray beam on the sample surface. Is set to an angle smaller than the critical angle of total reflection of X-rays, and a control mechanism is provided to automatically move the sample to a position where the scattered X-rays detected by the scattered X-ray intensity detector are minimized. To

Further, the total reflection X-ray analysis apparatus is housed in a vacuum container having a vacuum exhaust means, and the incident angle setting mechanism and the sample moving mechanism are operated while maintaining the degree of vacuum in the vacuum container. Provide a mechanism that can be operated from outside the container.

Further, the angle of incidence of the incident X-rays on the sample surface is set to be smaller than the critical angle of total reflection of X-rays, and the energy of the incident X-rays is continuously changed to obtain the energy of the X-ray reflectance. Provide a mechanism to measure the dependency.

Further, the fluorescent X-ray detector is provided so that the energy dependence of the fluorescent X-ray yield can be measured.

Furthermore, an electron detector is provided so that the energy dependence of the total electron yield can be measured.

Further, a diffracted X-ray detector is provided so that diffracted X-rays from the sample can be measured.

Further, a curved type position sensitive detector is used as the diffracted X-ray detector so that a plurality of diffracted X-rays from the sample can be simultaneously measured.

[0013]

In the above total reflection X-ray analyzer, a scattered X-ray detector for measuring the intensity of X-rays scattered from the sample, a mechanism for setting the incident angle of the incident X-ray beam to the sample at an arbitrary angle, and an X-ray detector A sample moving mechanism for moving the incident position of the line beam on the sample in a direction parallel to the X-ray beam, and
The incident angle of the incident X-ray beam on the sample surface is set to an angle smaller than the critical angle of total reflection of X-rays, and the scattered X-rays detected by the scattered X-ray detector are automatically set to a position where the scattered X-rays are minimized. By providing the control mechanism for moving the sample, it becomes possible to make all the incident X-ray beams incident on the sample surface and set the incident angle with good reproducibility. Therefore, even when the shape such as the thickness and the size is different for each sample to be measured, it is possible to perform the measurement with good reproducibility.

Further, the total reflection X-ray analysis apparatus is housed in a vacuum container having a vacuum exhaust means, and the incident angle setting mechanism and the sample moving mechanism are operated while maintaining the degree of vacuum in the vacuum container. By providing a mechanism that can be operated from outside the container, the incident angle of the incident X-ray on the sample surface is set to an angle smaller than the critical angle of total reflection of the X-ray, and the energy of the incident X-ray is continuously changed. By doing so, it becomes possible to measure the energy dependence of the X-ray reflectance.

Further, by providing the fluorescent X-ray detector, the energy dependence of the fluorescent X-ray yield can be measured.

Further, by providing an electronic detector,
It becomes possible to measure the energy dependence of the total electron yield.

Further, a diffracted X-ray detector is provided so that diffracted X-rays from the sample can be measured.

Further, a curved position sensitive detector is used as the diffracted X-ray detector so that a plurality of diffracted X-rays from the sample can be measured at the same time.

[0019]

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

(Embodiment 1) (1) Structure FIG. 1 is a block diagram of a total reflection X-ray analysis apparatus which is Embodiment 1 of the present invention. This device makes incident X-ray 1 incident on the sample 4 at a small incident angle less than the critical angle for total reflection and measures the energy dependence of the sample's X-ray reflectance, secondary electron yield, fluorescent X-ray yield, etc. is there.

The incident X-ray 1 has a 4-quadrant slit 2 and a width of 3 mm.
B. The height is shaped into about 50 μm, and the incident X-ray detector 3 is made to enter. An ionization chamber or the like is used as the incident X-ray detector 3.
The detector 3 is used to correct the intensity fluctuation of the incident X-ray 1. The incident X-ray 1 is absorbed by the detector 3 to some extent, but most of it passes through and is incident on the sample 5 fixed on the sample table 4. The sample table 4 has a vertical movement mechanism and a rotation mechanism having the sample surface as an axis in order to change the incident angle θ with respect to the incident X-ray 1. The intensity of the reflected X-ray 6 reflected on the surface of the sample 5 is measured by the reflected X-ray detector 7. If the entrance window of the detector 7 is made large enough, the X-ray 6 reflected by the sample 4 can be measured without moving the detector 7.
In this embodiment, the distance from the center of the sample to the entrance window of the reflection X-ray detector 7 is 300 mm, and the diameter of the entrance window is 15 mm, so that measurement can be performed within the range of θ <1.1 °. The X-ray scattered by the sample 5 is measured by the scattered X-ray intensity detector 11.
The fluorescent X-rays emitted from the sample 5 are the fluorescent X-ray detector 12
To measure. As the fluorescent X-ray detector 12, a semiconductor detector or the like having high energy resolution is used.

The sample moving mechanism and the X-ray detection system described above are controlled by a computer. The secondary electron detector is omitted in the figure.

FIG. 1 shows an example of an X-ray optical system used in this apparatus. The X-ray generated from an arbitrary X-ray source is monochromaticized by the monochromator 14, converged by the X-ray condensing mirror, then harmonics are removed by the X-ray reflecting mirror, and the slit 2 is made incident.

FIG. 2 is a side view of the first embodiment of the present invention.
The sample table 4 can rotate and move up and down around the incident X-ray beam 1, and the sample table 4 can be tilted to change the incident angle with respect to the incident X-ray 1. ing. Any of these operations can be performed from the outside of the vacuum container 20 while maintaining a high vacuum state. The operation mechanism and configuration of the sample table 4 provided inside the vacuum container 20 will be described below. Worm gear 2
Gears 2 and 23 are for rotating the sample 5, and the sample 5 placed on the sample table 4 can be rotated about the axis of the incident X-ray 1. The difference in rotation between the worm gears 22 and 23 is the bevel gear 2
The incident angle setting screw 26 is rotated through the engagement of 4 so that the sample stage 4 rotates about the fulcrum 21. This makes it possible to set the incident angle with respect to the incident X-ray 1 at a minute angle. The spring 32 is for stably pressing the sample table 4 against the base 27. Spur gears 28, 2
5 transmits the rotation to the worm gears 22 and 23, respectively. The spur gear 30 has a function of moving up and down the entire sample stage. The spur gear 30 is driven by an ultrahigh vacuum rotation introducing mechanism 31. The spur gears 28 and 29 are also driven by the rotation introducing mechanism for ultra-high vacuum, but they are omitted in the figure. The vacuum container 20 is placed on the stage. An interface for connecting to the incident X-ray detector 3 is connected to the X-ray source side of the vacuum container 20. The reflection X-ray detector 7 is attached to the vacuum container 20, and the secondary electron detector 13
Is installed. The stage is connected to a vertically movable apparatus frame through a tilt adjusting link and adjusted so that the axis of the incident X-ray and the optical axis of the entire apparatus coincide.

(2) Method for adjusting X-ray optical system and sample position FIG. 3 shows an outline of the X-ray optical system when synchrotron radiation is used as the X-ray source of the first embodiment of the present invention. In this embodiment, the distance from the two-crystal monochromator and the X-ray condensing mirror to the sample is set as long as 11 m to suppress the angular fluctuation of the X-ray beam incident on the sample. At this time, the divergence ε of the beam traveling direction of the X-ray beam depends on the X-ray optical system, and the total reflection angle φ of the X-ray focusing mirror, its total length, and the distance from the X-ray focusing mirror to the slit position. Determined from distance. When the width ΔS≈0 of the slit 2 in the vertical direction, ε is expressed by the following equations (Equation 1) and (Equation 2).

[0026]

[Number 1] ε = (500 × φ) / 10000 = 5 × φ × 10¯ 2 ... ( Equation 1) When set to, for example, φ = 6 × 10¯ ³ radians, epsilon =
3 × 10¯ is ^4. In addition, since the distance between the sample 5 and the slit 2 is 600 mm in this embodiment, the required sample length L is represented by the following equation, where the incident angle of X-rays on the sample 5 is θ.

[0027]

[Formula 2] L> (600 × ε + ΔS) / φ (mm) (Formula ² ) where ΔS = 50 μm, θ = 1 × 10 −2 (about 0.6
L) is 23 mm.

When the measurement is performed under the condition of total internal reflection as described above, the X-ray is irradiated onto a wide range of the sample surface because the X-ray is incident on the sample at a small incident angle. Therefore, unless the height and the incident angle of the sample are set with high accuracy, the X-ray 1 is incident on the side surface of the sample 5 or the sample table 4, and the reflectance and other measurement accuracy and reproducibility deteriorate. However, in practice, since the size, thickness, and shape of the warp and the like are different for each sample, it is difficult to set the position of the sample 5 with high accuracy only by the mechanical accuracy of the moving mechanism of the sample table 4.

However, in the present embodiment, the moving mechanism of the sample stage 4 and the scattered X-ray detector 9 are used, and the following (a) to (g) are used.
The sample can be set to the total reflection condition by the procedure up to.

(A) The sample stage 4 is sufficiently lowered so that the incident X-rays 1 are not incident on the sample 5 but all are incident on the reflected X-ray detector 7. At this time, the X-ray is not reflected on the sample, but the reflectance is defined as R = 1.0. The incident X-ray detector 3 is used to correct the fluctuation of the intensity of the incident X-ray 1.

(B) Raise the height of the sample table 4 until R = 0.5. The accuracy is set to about 0.1 μm.

(C) The incident angle dependency of the reflectance (for example, the incident angle range from -0.5 ° to about 1.5 °) is measured to determine the total reflection critical angle θc.

(D) The incident angle is set to a target value between 0 <θ <θc, for example, θ = 0.6 °.

(E) The scattered X-ray intensity is measured while changing the height of the sample table 4, and the relationship between the scattered X-ray intensity and the height of the sample table 4 is obtained.

(F) The height of the sample table 4 is set at the midpoint of the region where the scattered X-ray intensity measured in (e) is small. X-ray 1
Is not totally reflected, that is, when the X-ray 1 is incident on the side surface of the sample 5 or the sample stage 4, the scattered X-ray intensity becomes large. Means if you are.

(G) The above (c) and (b) are executed again.

By the above procedure, the automatic adjustment of the sample position at the target incident angle θ is completed.

When the incident angle of the X-ray 1 on the sample is θ and the refractive index of the sample 5 on the X-ray is n, the critical angle θc is

[0039]

[Mathematical formula-see original document] θc = √2 (1-n) ... (Equation 3), which is usually 0.2 ° to 0.6 ° for an X-ray having a wavelength of 0.15 nm. When θ <θc, total reflection occurs, but at this time, X-rays do not enter the substance at all, and waves exist along the surface. The depth at which the intensity becomes 1 / e is called the penetration depth. When θ << θc, it depends on the wavelength, for example, 3.2 nm for Si and 1.2 n for Au.
m. By measuring various characteristics under such total reflection conditions, it becomes possible to measure the ultrathin film or the surface.

(3) Measurement Example FIG. 4 is a diagram showing the angle dependence of the X-ray reflectance measured using a Si wafer having a length L = 40 mm in the traveling direction of the X-ray beam 1 as a sample. Further, FIG. 5 is a diagram showing the positional relationship between the X-ray beam and the sample for explaining FIG. 4. The position of the sample when measuring the symbols (a) to (e) in FIG.
It is shown in the diagram of the same symbols in FIG. (A) is the case of θ <0, and the incident X-ray 1 does not pass through the sample 5. (B) is the case of θ = 0, and only half of the incident X-ray 1 passes through. In (c), nearly 100% of the incident X-ray 1 is reflected.
From (c) to (e), the reflectance decreases as the incident angle increases. In this embodiment, the distance from the center of the sample 5 to the entrance window of the reflection X-ray detector 7 is 300 mm and the diameter of the entrance window is 15 mm, so that the measurement cannot be performed at an angle larger than (e).

FIG. 6 shows the reflectance R measured using this example.
It is an example of actual measurement of changes with respect to energy E (keV) of. In this spectrum, vibration occurs due to the anomalous dispersion of X-rays on the higher energy side than the absorption edge of the atoms contained in the sample surface. This vibrational structure is found in the X-ray absorption spectrum E
It is a phenomenon similar to the vibration structure called XAFS. The X-ray absorption spectrum can be approximately calculated from the reflectance spectrum by calculation. FIG. 7 is an example of an X-ray absorption spectrum calculated from the reflectance data of FIG.
A Fourier distribution function is obtained by Fourier transforming this spectrum. The array of other atoms around the X-ray absorbing atom can be analyzed from the radial distribution function. FIG. 8 shows Si and SiO ₂ calculated from the above X-ray absorption spectrum.
3 is an example of a radial distribution function of.

As described above, the use of this embodiment makes it possible to analyze the primitive level structure of the sample surface.

At the same time, the composition of the sample surface can be analyzed by analyzing the energy of the fluorescent X-rays measured by the fluorescent X-ray detector with a multi-channel analyzer.

Example 2 (1) Structure FIG. 9 shows the configuration of Example 2 of the present invention. In this embodiment, X
The difference from the first embodiment is that the line detector 11 is provided. The X-ray optical system upstream of the four-quadrant slit 12 is the same as that in the first embodiment. As the diffracted X-ray detector 11, a curved type position sensitive X-ray detector for ultra-high vacuum is used. A semiconductor detector is used as the scattered X-ray detector 9. In this embodiment, the sample surface is held in the vertical direction, and horizontal movement in the X, Y, and Z directions shown in the drawing and rotation around the Z axis and the Y axis are possible.

FIG. 10 shows a top view of the sample stage portion of this embodiment. The sample table 4 is housed in a vacuum container 20 having an ultrahigh vacuum atmosphere. At the time of sample exchange, both the sample table 4 and the moving mechanism are moved to the sample exchange chamber 36. The sample exchange chamber 36 is also in a high vacuum atmosphere.

(2) Measurement example Regarding the X-ray reflectance, EXAFS measurement and fluorescent X-ray analysis, the same results as in Example 1 can be obtained. The feature of the second embodiment is that X-ray diffraction can be measured by using a curved position sensitive detector. FIG. 11 shows an example of measurement of X-ray diffraction on the sample surface using the total reflection method. The one-dimensional two-dimensional lattice on the surface becomes a reciprocal lattice rod in reciprocal space. The diffraction spot appears in the direction from the center of the Ewald sphere toward the intersection of the reciprocal rod and the Ewald sphere, and the diffraction intensity is equal at any position on the rod. If the crystal is set in such an orientation that a plurality of reciprocal lattice rods intersect the Ewald sphere at the same time, a plurality of diffraction spots as shown in FIG. 11 can be simultaneously measured by the curved position sensitive detector.

[0047]

According to the present invention, under the condition of total internal reflection, X
When measuring the energy dependence of the linear reflectance, the incident position and the incident angle can be automatically set with good reproducibility, and highly accurate measurement can be performed. Even when the shape such as the thickness or the size is different for each sample, it is possible to set the position with good reproducibility. This enables highly accurate measurement of X-ray scattering, X-ray diffraction, EXAFS, fluorescent X-rays, etc. on the interface / surface of multi-layer thin films used for semiconductor devices, etc. to analyze the atomic / molecular arrangement of materials or ultra-trace analysis of the surface. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a principle diagram showing a configuration of a total reflection X-ray analysis apparatus according to a first embodiment of the present invention.

FIG. 2 is a side view of a sample stage portion of the total internal reflection X-ray analysis apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of an X-ray optical system when synchrotron radiation light is used as an X-ray source in the total internal reflection X-ray analysis apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the X-ray reflectance of the surface of a silicon wafer and the X-ray incident angle measured by using the total-reflection X-ray analyzer of Example 1 according to the present invention.

5 is a principle diagram showing the positional relationship between the X-ray beam and the sample in the diagram showing the relationship between the X-ray reflectance and the X-ray incident angle in FIG.

FIG. 6 is a diagram showing the relationship between X-ray reflectance and X-ray photon energy measured using the total internal reflection X-ray analyzer of Example 1 according to the present invention.

7 is a diagram showing a relationship between an X-ray absorption coefficient and X-ray photon energy obtained from the relationship between the X-ray reflectance and X-ray photon energy in FIG.

FIG. 8 is a diagram of a radial distribution function of Si and SiO ₂ calculated from FIG. 6.

FIG. 9 is a principle diagram showing the configuration of a total reflection X-ray analysis apparatus according to a second embodiment of the present invention.

FIG. 10 is a side view of a sample stage portion of a total reflection X-ray analysis apparatus according to a second embodiment of the present invention.

FIG. 11 is a measurement view of X-ray diffraction of the surface measured by using the total reflection X-ray analyzer of Example 2 according to the present invention.

[Explanation of symbols]

 1 ... Incident X-ray, 2 ... 4-quadrant slit, 3 ... Incident X-ray detector, 4 ... Sample stage, 5 ... Sample, 6 ... Reflected X-ray, 7 ... Reflected X-ray detector, 8 ... Scattered X-ray, 9 ... scattered X-ray detector, 10 ... diffracted X-ray, 11 ... diffracted X-ray detector, 12 ... fluorescent X-ray detector, 13 ... electron detector, 14 ... monochromator, 15 ... X-ray condensing mirror, 16 ... X-ray reflecting mirror, 20 ... Vacuum container, 21 ... Support point, 22, 23 ... Worm gear, 24, 25 ... Bevel gear, 26 ... Screw, 27 ... Base, 28, 29, 30 ... Flat gear, 31 ... Rotation introducing mechanism, 32 ... Spring, 33 ... Window, 34 ... XZ stage, 35 ... Incident angle setting mechanism, 36 ... Sample exchange chamber.

Claims (10)

[Claims] 1. An incident X-ray detector and a reflected X-ray detector,
In a total reflection X-ray analyzer for measuring the reflectance of X-rays incident on the surface of a sample placed on a sample table, a scattered X-ray detector for measuring the intensity of X-rays scattered from the sample, and an incident X-ray beam A mechanism to set the incident angle to the sample at an arbitrary angle,
A total reflection X-ray analysis apparatus comprising: a sample moving mechanism for moving the incident position of the X-ray beam on the sample by changing the distance between the X-ray beam and the sample surface. 2. The total reflection X-ray analysis apparatus according to claim 1, wherein the total reflection X-ray analyzer is housed in a vacuum container having a vacuum evacuation means, and the incident angle setting mechanism and the sample moving mechanism are operated to maintain the degree of vacuum in the vacuum container. At the same time, a total reflection X-ray analysis apparatus is provided with a mechanism that can be operated from outside the vacuum container. 3. The scattered X-ray detected by the scattered X-ray intensity detector according to claim 1, wherein the incident angle of the incident X-ray on the sample surface is set to be smaller than the critical angle of total reflection of X-ray. A total internal reflection X-ray analyzer characterized by comprising a control mechanism for taking optimum total internal reflection conditions by automatically moving the sample to a position where the line is minimized. 4. The method according to claim 1, further comprising a sample moving mechanism in the XY direction parallel to the sample surface, and a mechanism capable of measuring distribution of various characteristics on the sample surface. Reflective X-ray analyzer. 5. The incident angle of the incident X-ray on the sample surface according to claim 1 or 2, which is smaller than the critical angle of total reflection of X-ray, and the energy of the incident X-ray is continuously changed. A total reflection X-ray analysis apparatus comprising a mechanism capable of measuring the energy dependence of X-ray reflectance. 6. The mechanism according to claim 1, further comprising a fluorescent X-ray detector, and a mechanism for spectroscopically measuring fluorescent X-rays generated from the sample and performing fluorescent X-ray analysis of the sample. Total reflection X-ray analyzer. 7. The total reflection X-ray analysis apparatus according to claim 5, further comprising a fluorescent X-ray detector and a mechanism capable of measuring the energy dependence of the fluorescent X-ray yield. 8. The total reflection X-ray analysis apparatus according to claim 5, further comprising an electron detector and a mechanism capable of measuring the energy dependence of the total electron yield. 9. The total internal reflection X-ray analysis apparatus according to claim 1, further comprising a mechanism for measuring a diffracted X-ray from a sample by including a diffracted X-ray detector. 10. The total reflection X-ray according to claim 9, wherein a curved position sensitive detector is used as the diffraction X-ray detector, and a mechanism capable of simultaneously measuring a plurality of diffraction X-rays from the sample is provided. Analysis equipment.