JPH11337507A - X-ray reflectance measuring method, and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray reflectance measuring device, which can evaluate the structure in a micro-area of a test sample when the surface of the test sample is irradiated with X-ray and a reflectance of X-ray reflected on the surface of the test sample is measured to evaluate the structure of the test sample. SOLUTION: A crystalline 2 consisting of powder whose particle diameters are uniform is sprayed on the surface of a measured test sample 1. An X-ray from an X-ray generating device 3 arranged on the surface side of the measured test sample 1 is cast on the crystalline 2 via a collimator 4 comprising slits 4a and 4b. The X-ray cast on the crystalline 2 is diffracted by the crystalline 2 and is made incident on the surface of the measured test sample 1 at a small angle with respect to the surface of the measured test sample 1 to make total reflection on the surface of the measured test sample 1. The X-ray diffracted by the crystalline 2 is made incident on the measured test sample 1 thus, the width of an X-ray irradiated area on the surface of the measured test sample 1 is lessened. The X-ray reflected on the surface of the measured test sample 1 passes through a slit 7 and a monochromator 6 and an X-ray detector detects the X-ray.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray reflectivity measuring method and an X-ray reflectivity measuring apparatus, and more particularly, to an X-ray reflectivity measuring method and an X-ray reflectivity measuring method for evaluating the structure of a sample using X-rays. The present invention relates to a linear reflectance measuring device.

[0002]

2. Description of the Related Art As one of methods for analyzing a sample of an ultra-thin film or a multilayer film, an X-ray reflectivity measuring method utilizing X-ray reflectivity is used. In the X-ray reflectivity measuring method using the X-ray reflectivity, an X-ray having a wavelength of about 1 ° is irradiated on the surface of the sample, and the irradiated X-ray is optically specularly reflected on the surface of the sample. In the state where the sample is irradiated with the X-rays, the sample is rotated, for example, and the angle dependence of the intensity of the X-rays reflected on the surface of the sample, that is, the dependence of the incident angle or the emission angle is measured. Then, based on the complex index of refraction and Fresnel's formula, an analysis is performed on the portion of the sample irradiated with X-rays.

When a sample has a thin film, X-rays reflected at respective interfaces of the thin film and X-rays reflected at the surface of the sample interfere with each other. In this case, an interference pattern is obtained in which the reflectivity of X-rays at the interface reflects the thickness of each layer of the sample. In addition, when the surface or the interface of the sample has irregularities (roughness), the roughness affects the reflectivity of X-rays on each surface. Therefore, the thickness of each layer of the sample, the density and composition of each layer of the sample, the roughness of each interface of the sample, and the like can be obtained by using a mathematical formula relating to the reflectivity of X-rays that takes in these phenomena.

[0004] A thin film having a thickness of 1 nm to several 100 nm can be evaluated nondestructively by the X-ray reflectivity measuring method using X-rays described above.

[0005] As an example of an X-ray reflectivity measuring method and an X-ray reflectivity measuring apparatus utilizing X-ray reflectivity which are currently generally performed, [TCHuang, W. Parrish, Adv.
y Anal. 35, 137 (1992)]. Figure 2 shows [TCHuang, W.Parrish, Adv. .X-ray Anal.35,
137 (1992)] is a schematic view showing an outline of the X-ray reflectivity measuring apparatus described in [137].

In the conventional X-ray reflectivity measuring apparatus, as shown in FIG. 2, a slit 32 and a channel cut monochromator 3 are arranged in the traveling direction of the X-ray emitted from the X-ray source 31.
3, a slit 34, a sample 35, a slit 36, a channel cut monochromator 37, a slit 38, and an X-ray detector 39 are arranged in this order from the X-ray source 31 side. As the X-ray source 31, a rotating anti-cathode or the like is used.
The channel cut monochromator 33 is for making the X-ray incident on the channel cut monochromator 33 monochromatic and parallel. The channel cut monochromator 37 is for removing scattered X-rays and fluorescent X-rays from X-rays incident on the channel cut monochromator 37. As the X-ray detector 39, a scintillation counter or the like is used. The surface of the sample 35 is flat, and X-rays are incident on the surface.

[0007] Of the X-rays emitted from the X-ray source 31, the slit 32 and the channel cut monochromator 33
X-rays that have passed through are converted to monochromatic and collimated by the slit 32 and the channel cut monochromator 33. The monochromatic and parallelized X-rays pass through the slit 34 and have a small angle θ with respect to the surface of the sample 35.
_{The light} enters the surface of the sample 35 at _i . Thus to the surface of the sample 35, the incident angle theta _i angle X-rays formed by the traveling direction of the X-rays incident on the surface. This incident angle θ _i is
When the total angle becomes smaller than the critical angle for total reflection θ _{c at} 5, the X-rays are optically totally reflected on the surface of the sample 35. The value of the critical angle for total reflection θ _c depends on the refractive index of the sample 35.

The X-rays reflected by the sample 35 pass through the slit 36 and the channel cut monochromator 37, whereby X-rays unnecessary for measurement, such as scattered X-rays and fluorescent X-rays, are removed. The X-rays that have passed through the slit 36 and the channel cut monochromator 37 enter the X-ray detector 39 after passing through the slit 38, and the intensity of the X-ray is measured by the X-ray detector 39. And X
Using the X-ray intensity measured by the X-ray detector 39, X
Calculate the reflectance of the sample 35 for the line.

[0009] The critical angle when the surface of the sample 35 is irradiated with X-rays is determined by the refractive index of the sample 35, which depends on the electron density of the constituent material. The critical angle changes accordingly. As the angle θ shown in FIG. 2 increases and the incident angle θ _i of the X-ray increases, the X-ray gradually penetrates deeper into the sample 35, and in a substance having an ideal plane, the incident angle θ _i is critical. When the angle becomes larger than the angle θ _c , the reflectivity of the X-ray sharply decreases in proportion to θ _i ^-4 .

When a thin film made of another material having a different electron density from the substrate is laminated on the substrate with a uniform thickness as the sample 35, the interface between the substrate and the thin film,
The X-rays reflected on the surface of the thin film strengthen or weaken each other, and a vibration pattern due to interference of the X-rays appears on the reflectance curve of the X-rays. Then, the thickness of the thin film of the sample 35 can be examined from the period of the vibration pattern, and information on the interface between the substrate and the thin film and the surface of the thin film can be obtained from the angular dependence of the amplitude of the vibration pattern. Also, by using both the period and amplitude of the vibration pattern,
The density of the thin film formed on the sample 35 can be obtained.

[0011]

However, in the above-mentioned conventional X-ray reflectivity measuring apparatus, the incident angle of the X-ray is set near the critical angle in order to reflect the X-ray with a finite reflectivity. However, this critical angle is very small. For example, the critical angle on a glass plate for X-rays of CuKα is 0.1 mm.
22 °. For this reason, when a strong rotating anti-cathode X-ray source is used as an X-ray source used in a laboratory or the like, the width of the X-ray is set to 50 μm immediately before irradiating a sample with a slit or the like.
Even if it is limited to a degree, the size of the X-ray irradiation area on the sample when incident near the critical angle becomes several cm. Even if a microbeam is formed using a high-intensity light source such as synchrotron radiation, the size of the X-ray irradiation area on the sample is limited to about several mm, and the X-ray is applied to a smaller area. It is impossible to perform measurement by irradiation. Therefore, it has been considered impossible to evaluate a difference in reflectance in a minute area of a sample by the conventional technique.

An object of the present invention is to measure the intensity of X-rays reflected by a sample when the sample is irradiated with X-rays and the angle dependence of the intensity to evaluate the structure of the sample. It is an object of the present invention to provide an X-ray reflectivity measuring method and an X-ray reflectivity measuring apparatus capable of measuring the reflectivity of a sample to evaluate the structure of a minute region of a sample.

[0013]

In order to achieve the above object, an X-ray reflectivity measuring method according to the present invention provides a method for measuring the intensity of X-rays reflected by a sample when the surface of the sample is irradiated with the X-rays; By measuring the angle dependence of the intensity of the sample,
In the X-ray reflectivity measuring method for evaluating the structure of a portion irradiated with the X-ray, a step of disposing a crystal in the vicinity of the surface of the sample, a step of generating X-rays,
Collimating a line, diffracting at least a part of the collimated X-rays by the crystal to obliquely enter the surface of the sample, and X-rays reflected on the surface of the sample. Detecting and measuring the intensity of the X-ray and the angle dependence of the intensity.

In the above invention, after the generated X-rays are collimated, at least a part of the collimated X-rays is diffracted by a crystal arranged near the surface of the sample, so that the X-rays are obliquely applied to the surface of the sample. Incident on Here, when irradiating the surface of the sample with X-rays at a small angle with respect to the surface of the sample so that the X-rays are totally reflected on the surface of the sample, the X-ray diffracted on a specific crystal plane of the crystal is By irradiating the sample, the width of the X-ray irradiation area on the surface of the sample can be reduced. Therefore, X-rays are irradiated on a minute area on the sample surface, and the X-rays reflected on the minute area are detected to measure the intensity of the X-rays and the angle dependence of the intensity. The structure of the minute region of the sample can be evaluated by determining the reflectivity of the line. As a result, an X-ray reflectivity measuring method capable of evaluating the structure of a minute region of a sample, which has been impossible with the related art, is realized.

Further, as the crystal, the particle diameter is 10n.
It is preferable to use a powder having a size of m to 10 μm.

As described above, the crystalline material has a particle diameter of 10
By using a powder having a size of not less than 10 nm and not more than 10 μm, when diffracting X-rays by the crystal and irradiating the X-rays to the surface of the sample, at a desired angle with respect to the surface of the sample, and X-rays can be emitted with the width of the irradiation area smaller than several mm. Particle size of powder is about 10μ
When it is larger than m, the directions satisfying the diffraction condition of the powder become discrete, and it may become impossible to make X-rays incident on the surface of the sample at a desired angle. On the other hand, when the particle diameter of the powder is smaller than about 10 nm, the beam itself of the diffraction line generated by diffracting the X-ray by the powder has a finite spread that cannot be ignored, and the X-ray reflected on the surface of the sample.
This is inconvenient because the angular resolution when detecting a line is reduced.

Further, the X-ray reflectivity measuring apparatus of the present invention
When the surface of the sample is irradiated with X-rays, the intensity of the X-rays reflected by the sample and the angle dependence of the intensity are measured to evaluate the structure of the portion of the sample irradiated with the X-rays. X-ray reflectivity measuring apparatus for generating X-rays, parallelizing means for parallelizing X-rays from the X-ray generating means, and an X-ray reflectivity measuring apparatus arranged near the surface of the sample. A crystal which diffracts at least a part of the X-rays collimated by the parallelizing means and makes the X-ray obliquely incident on the surface of the sample, the intensity of the X-ray reflected by the sample, and the angle dependence of the intensity. X-ray detecting means for detecting the X-rays to measure the properties.

In the above invention, the above-described X-ray reflectivity measuring method is used, and the X-ray reflectivity is applied to the surface of the sample at a small angle with respect to the surface of the sample so that the X-ray is totally reflected on the surface of the sample. By irradiating the sample with X-rays diffracted on a specific crystal plane of the crystal, the width of the X-ray irradiation region on the surface of the sample can be reduced. Therefore, in the same manner as described above, X-rays are irradiated to a minute region on the sample surface, and the X-rays reflected from the minute region are detected to measure the intensity of the X-rays and the angle dependence of the intensity. Thus, the structure of the minute region of the sample can be evaluated by determining the X-ray reflectivity in the minute region. As a result, an X-ray reflectometer capable of evaluating the structure of the minute region of the sample is obtained.

Further, the crystalline material has a particle diameter of 10
It is preferable to use powder having a size of not less than nm and not more than 10 μm.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram for explaining an X-ray reflectance measuring apparatus according to one embodiment of the present invention.

In the X-ray reflectometer of the present embodiment, as shown in FIG. 1, a crystal 2 is arranged on the surface of a measurement sample 1. Using quartz glass as the material of the measurement sample 1,
On the surface of the measurement sample 1, as a crystal 2, a particle size of about 2
μm aluminum nitride powder was evenly sprayed. With a scanning electron microscope, the particle size and distribution of the aluminum nitride powder sprayed on the surface of the measurement sample 1 can be observed.

The measurement sample 1 may be a single-layer film or a multi-layer film.

It is preferable that the crystal 2 is a powder having a uniform particle diameter and a small crystal orientation. The crystal powder constituting the crystal 2 needs to be uniformly distributed on the measurement sample 1 as described above. Crystal 2
The following conditions are required for the crystal grain size of.

When the crystallite diameter of the crystal 2 is larger than several μm or the orientation of the crystal is large, the directions satisfying the diffraction condition become discrete, so that the X-rays are applied to the surface of the measurement sample 1. In some cases, the light cannot be incident at a desired angle, which is inconvenient. On the other hand, if the crystallite diameter of the crystal body 2 is smaller than about several nm, the beam of the diffraction line itself has a finite spread that cannot be ignored. Therefore, when the X-rays reflected on the surface of the measurement sample 2 are detected. Is disadvantageous in that the angular resolution is reduced. Thus, the particle diameter of the crystal 2 is set to be in the range of 10 nm to 10 μm. When the crystal 2 is placed on the measurement sample 1,
The orientation should be eliminated as much as possible.

As a specific method for disposing the crystal 2 on the measurement sample 1, there is a method in which a solvent in which the crystal powder is dissolved is applied on the measurement sample 1 by spin coating or the like, and the applied solvent is dried. . Alternatively, a method of applying an organic solvent or the like in which the crystalline powder is dissolved on the measurement sample 1 by spray coating or the like may be used. In addition to these methods,
Any method may be used as long as the method can form the crystal 2 while satisfying the above conditions.

The measurement sample 1 is attached to a goniometer (not shown) that rotates the measurement sample 1 about an axis perpendicular to the surface of the measurement sample 1. The measurement sample 1 is rotated by a goniometer in order to measure the angle dependence of the X-ray reflectivity of the measurement sample 1.

An X-ray generator 3 as X-ray generating means for generating X-rays is arranged on the surface side of the measurement sample 1. The X-ray generator 3 generates X-rays for irradiating the crystal 2 on the surface of the measurement sample 1.

As the X-ray generator 3, a rotating anti-cathode X-ray tube using Cu as a negative electrode was used. The rotating anti-cathode X-ray tube was driven at a tube voltage of 40 kV and a tube current of 300 mA, and the X-ray focal point of the X-ray generator 3 was set as a line focus.

Between the X-ray generator 3 and the measurement sample 1,
Collimator 4 composed of slits 4a and 4b
Is arranged. The slits 4a and 4b are arranged in this order from the X-ray generator 3 side.
The slit width of each of a and 4b is 50 μm. 400 mm between the slits 4a and 4b
And the distance between the slit 4b and the measurement sample 1 is 100
mm. The diffraction peak on the (100) plane of aluminum nitride constituting crystal 2 is observed at an angle 2θ _b of 33.216 ° with respect to CuKα X-rays. Here, when there is no crystal 2 on the surface of the measurement sample 1, the angle w at which the X-rays emitted from the X-ray generator 3 and passing through the collimator 4 enter the surface of the measurement sample 1 is set to approximately 33 °. Set. Thus, the X-ray diffracted on the (100) plane of the aluminum nitride is incident on the quartz glass surface of the measurement sample 1 at a small incident angle.

In such an arrangement, a part of the X-rays from the X-ray generator 3 are diffracted by the crystal 2 and irradiated on the surface of the measurement sample 1.
The divergence angle of the line was about 0.25 mrad (about 0.014 °), and the width of the X-ray irradiation area on the surface of the measurement sample 1 was about 130 μm.

A detection system 9 is arranged in the traveling direction of X-rays reflected by the measurement sample 1 after being diffracted by the crystal 2. The detection system 9 includes a slit 7 and a monochromator 6 arranged in order from the measurement sample 1 side, and a monochromator 6.
And an X-ray detector 5 for detecting the X-ray reflected by the. The slit width of the slit 7 is 50 μm,
The distance between the slit 7 and the measurement sample 1 was 200 mm.

The monochromator 6 is provided with a fluorescent X-ray and a scattered X-ray.
The X-ray detector 5 removes the X-rays and prevents the X-rays from being incident on the X-ray detector 5. A monochromator 6 is appropriately disposed between the slit 7 and the X-ray detector 5. As the monochromator 6, a graphite monochromator was used, and as the X-ray detector 5, a scintillation counter was used. The angular resolution of the detection system 9 is about 0.25 mrad
(About 0.014 °).

The slit 7 is for achieving the above-mentioned angular resolution of the detection system 9.
Usually, a slit width of about 50 μm or less may be used.

The monochromator 6 is provided with a fluorescent X-ray and a scattered X-ray.
The purpose is to remove the X-rays and prevent the X-rays from being incident on the X-ray detector 5.

Here, the X-ray reflectivity was measured, and the measurement sample 1 was measured.
Is required to have an angular accuracy of about (1/1000) °. For this purpose, X irradiating the measurement sample 1
Lines are required to be monochromatic and parallel. In an X-ray reflectometer used in an ordinary laboratory system, since the X-ray used is a divergent beam, a monochromator or the like is arranged between the X-ray generator 3 and the measurement sample 1, and the X-ray generator is used. X-rays may be made monochromatic and parallelized.

Next, a specific procedure of the X-ray reflectivity measuring method will be described.

First, a powder of aluminum nitride as the crystal 2 is arranged on the surface of the measurement sample 1 as uniformly as possible and not oriented.

Next, the Bragg angle θ _b of the powder of crystal 2
Measurement. In the measurement of the Bragg angle theta _b includes an optical system and using a conventional focusing method, and may also be any one of an optical system using the parallel beam method. When the thickness of the crystal 2 is small, X-rays from the X-ray generator 3 are obliquely incident on the measurement sample 1 at a fixed angle, and the X-ray detector 5 is scanned. In a typical diffraction crystalline powder, in order to overlap the peak occurs at a large angle side, the diffraction angle with a clear peak in the low angle side, that accurately determine the Bragg angle theta _b.

The measurement sample 1 is irradiated with X-rays from the X-ray generator 3 at the Bragg angle θ _b of the powder of the crystal 2 obtained by the above operation. In order to measure the reflectance of X-rays in a minute area in the measurement sample 1, the X-rays from the X-ray generator 3 are limited to a small area by the collimator 24.

The intensity of the X-rays generated by the X-ray generator 3 is determined while appropriately adjusting the intensity so that sufficient intensity can be obtained in the analysis of the reflectivity of the X-rays. The X-rays thus miniaturized by the collimator 4 are incident on the crystal powder of the crystal 2. The X-rays incident on the crystal 2 are diffracted by a specific surface of the crystal powder of the crystal 2, and the diffracted X-rays are incident on the surface of the measurement sample 1. The X-rays incident on the measurement sample 1 are reflected by the measurement sample 1, and the reflected X-rays pass through the slit 7, pass through the monochromator 6, and are detected by the X-ray detector 5. In this manner, the X-ray is detected by the X-ray detector 5, and the intensity of the X-ray is measured and recorded.

Then, the measurement sample 1 is rotated by a fixed angle around the center axis of the goniometer to which the measurement sample 1 is attached, and the detection system 9 is turned around the center axis of the goniometer. The detection system 9 is scanned. At this time, among the X-rays reflected on the surface of the measurement sample 1, X-rays in a range where the angle α formed between the traveling direction of the X-ray and the surface of the measurement sample 1 is about 0 ° to 5 ° are measured. By repeating the measurement of the X-ray, an angular distribution of the intensity of the X-ray reflected by the measurement sample 1 is obtained.

Next, based on the measurement results, the horizontal axis represents the angle and the vertical axis represents the reflectance as a relationship between the angle between the X-ray and the surface of the sample 1 and the reflectivity of the X-ray. And simulate. Thus, the thickness, density, composition, roughness, and the like of the film in the minute region of the measurement sample 1 can be obtained. As an analysis algorithm or the like for obtaining these physical property values, an equation based on the complex refractive index and Fresnel equation, a Fourier analysis method, or the like is used.

In the present embodiment, the reflection X obtained by the measurement
When the analysis was performed based on the linear intensity curve, the information of a minute region having a width of 130 μm on the surface of quartz constituting the measurement sample 1 was found to have a density of 2.20 g / cm ³ and a surface roughness of 0.2 μm.
A value of 7 nm was obtained.

As described above, in the present embodiment,
After the X-rays generated by the X-ray generator 3 are collimated by the collimator 4, the collimated X-rays are diffracted by the crystal 2 arranged near the surface of the measurement sample 1, and the diffracted X-rays
A part of the diffracted X-ray is obliquely incident on the surface of the measurement sample 1 so that a part of the line is totally reflected on the surface of the measurement sample 1. When X-rays are irradiated on the surface of the measurement sample 1 at a small angle with respect to the surface of the measurement sample 1 so that the X-rays are totally reflected on the surface of the measurement sample 1, the X-rays are diffracted on a specific crystal plane of the crystal 2. By irradiating the measurement sample 1 with the X-rays
Can reduce the width of the X-ray irradiation area on the surface. Therefore, by irradiating a small area on the surface of the measurement sample 1 with X-rays, detecting the X-rays reflected on the small area, and measuring the intensity of the X-rays and the angle dependence of the intensity, the X-rays are irradiated. The structure of the minute region of the measurement sample 1 can be evaluated by calculating the reflectance of the X-ray. As a result, an X-ray reflectometer capable of evaluating the structure of a minute region of a sample, which has been impossible with the related art, is obtained.

[0046]

As described above, according to the present invention, when X-rays are irradiated on the surface of a sample at a small angle with respect to the surface of the sample so that the X-rays are totally reflected on the surface of the sample, By irradiating the sample with X-rays diffracted on a specific crystal plane, the width of the X-ray irradiation region on the surface of the sample can be reduced. Therefore, by obtaining the reflectance of X-rays in a minute area of the sample, it has been impossible with the conventional technology.
There is an effect that it becomes possible to evaluate the structure of the minute region of the sample.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an X-ray reflectance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an outline of an X-ray reflectance measuring apparatus according to a conventional technique.

[Explanation of symbols]

1 measurement sample 2 crystal 3 X-ray generator 4 collimator 4a, 4b, 7 slit 5 X-ray detector 6 monochromator 9 detection system theta _i incident angle: angle between the traveling direction and the sample surface of the X-ray theta _c Critical angle of total reflection (angle measured by the same measurement as incident angle) θ _b Bragg angle (angle measured by the same measurement as incident angle) w Incident angle α outgoing angle

Claims (4)

[Claims] 1. A portion of the sample irradiated with the X-rays by measuring the intensity of the X-rays reflected by the sample when the surface of the sample is irradiated with the X-rays and the angle dependence of the intensity. An X-ray reflectivity measuring method for evaluating the structure of (a), wherein: disposing a crystal in the vicinity of the surface of the sample; generating X-rays; parallelizing the X-rays; Diffracting at least a portion of the X-rays by the crystal and obliquely incident on the surface of the sample; detecting X-rays reflected on the surface of the sample, detecting the intensity of the X-rays, Measuring the angle dependence of the intensity. 2. The X-ray reflectance measurement method according to claim 1, wherein a powder having a particle diameter of 10 nm or more and 10 μm or less is used as the crystal. 3. A portion of the sample irradiated with the X-rays by measuring the intensity of the X-rays reflected by the sample when the surface of the sample is irradiated with the X-rays and the angle dependence of the intensity. An X-ray reflectivity measuring device for evaluating the structure of (1), comprising: X-ray generating means for generating X-rays; parallelizing means for parallelizing X-rays from the X-ray generating means; A crystal that is diffracted at least part of the X-rays collimated by the collimating means and is obliquely incident on the surface of the sample, and the intensity of the X-rays reflected by the sample, An X-ray reflectivity measuring device comprising: an X-ray detecting means for detecting the X-ray in order to measure the angle dependence of the intensity. 4. The X-ray reflectometer according to claim 3, wherein a powder having a particle diameter of 10 nm or more and 10 μm or less is used as the crystal.