JPH11237229A - Surface-interface roughness measuring method and measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure unevenness on a specimen surface or an interface between regions different in refractive index by distinguishing the unevenness from composition change when it exists in a measurement object region. SOLUTION: This measuring method makes X rays 2 having coherency monochromatic, and irradiates the surface or the thickness direction of a specimen to be measured with X rays 6 which are made monochromatic and different in wavelength, at the same visual oblique angle, by adjusting a visual oblique angle in such a manner that selective reflection is generated on the interface between regions different in refractive index. X rays 9 having the respective wavelengths which are reflected by the specimen to be measured are recorded as scattered images in a recording medium 10. From correlation of the respective scattered images corresponding to the respective wavelengths which are recorded in the recording medium, unevenness on the surface of the specimen 8 to be measured or the interface between regions is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring surface and interface roughness, and more particularly to a method and an apparatus capable of non-destructively measuring fine irregularities on the order of angstroms.

[0002]

2. Description of the Related Art As a method for non-destructively measuring minute irregularities on the order of angstroms using X-rays, a method using reflectance or CTR (Crystal Truncation Rod) scattering has been conventionally known. However, since the X-rays usually do not have the same wavelength and phase, if there is a composition variation in the measurement target area, the composition variation and the unevenness of the sample are measured as one, and the composition variation and the unevenness are distinguished. Can not do.

[0003]

As described above, when it is attempted to measure unevenness using conventional X-rays, it is not possible to distinguish between composition fluctuation and unevenness, so that the interface between the sample surface and the region having a different refractive index is not possible. However, there was a problem that it was not possible to measure the irregularities of the sample accurately.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to accurately measure unevenness of a sample surface or an interface between regions having different refractive indices even if there is a composition variation in a measurement target region. It is an object to provide a simple measuring method and a measuring device.

[0005]

According to the surface / interface roughness measuring method of the present invention, a monochromatic X-ray having coherence is converted into monochromatic X-rays having different wavelengths, and the surface or thickness of the sample is measured. The oblique angle is adjusted so that the light is selectively reflected at the interface between the regions having different refractive indices in the directions. Is recorded in the recording means, and the corrugation of each image corresponding to the X-rays of each wavelength recorded in the recording means is used to obtain the surface or interface irregularities of the sample to be measured.

[0006] The surface / interface roughness measuring apparatus according to the present invention comprises:
Wavelength selecting means for monochromaticizing the X-ray having coherence to select a desired wavelength, and a viewing angle for irradiating the sample to be measured with the X-ray of the wavelength selected by the wavelength selecting means at a desired viewing angle. Angle adjusting means, and X-rays radiated on the sample at the oblique angle adjusted by the oblique angle adjusting means and selectively reflected at an interface between surfaces of the sample or regions having different refractive indices in the thickness direction. Recording means for recording an image obtained by the method, and means for determining the surface or interface unevenness of the sample to be measured from the correlation between the images corresponding to X-rays of different wavelengths recorded on the recording means. And

According to the invention, the coherent X-ray is monochromatic (obtained as a single-wavelength X-ray having the same wavelength and phase), and the viewing angle (between the sample surface and the incident X-ray). Angle) (preferably adjusted to a viewing angle near the total reflection condition) by selectively reflecting X-rays at the sample surface or at the interface between regions having different refractive indices.
Even if there is a composition variation in the measurement target area, a pattern reflecting the X-ray coherence based on the unevenness can be obtained as a scattered image. However, since only a single wavelength X-ray can obtain a pattern due to interference but cannot obtain a pattern corresponding to the unevenness itself, each scattering obtained by separately irradiating X-rays of at least two or more different wavelengths can be obtained. The images are respectively recorded in the recording means, and irregularities are obtained from the correlation of each scattered image. According to such a method, even if there is a composition variation near the sample surface or the interface which is the measurement target area, it is possible to accurately measure minute irregularities on the surface or the interface in the angstrom order, distinguished from the composition variation. .

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of a surface / interface roughness measuring apparatus according to the present invention.

Reference numeral 1 denotes a storage ring, which has a coherent X
To generate line 2. Although the storage ring 1 acts as a semi-coherent light source, a coherent light source such as a free electron laser can be used instead of the storage ring 1. Reference numerals 3a and 3b denote crystal monochromators in which, for example, (111) silicon is symmetrically arranged.
The line 4 is made monochromatic. Reference numerals 5a and 5b denote slits for extracting only a central portion of the X-rays 4 from the crystal monochromators 3a and 3b to form an X-ray beam 6 having higher directivity and coherence. Reference numeral 7 denotes a holder on which the sample 8 to be measured is mounted. The holder 7 adjusts the angle of the mounting surface with a goniometer (not shown) to thereby form an angle between the mounting surface and the X-ray beam 6 (X incident on the sample surface and X-ray beam). The angle formed by the line (oblique angle) is adjusted to a desired angle. A recording medium 10 records the X-rays 9 scattered and reflected from the sample 8 to be measured as a scattered image. Numeral 11 denotes an arithmetic unit for obtaining the unevenness of the surface area of the sample 8 to be measured from the correlation between two scattered images by X-rays having different wavelengths recorded on the recording medium 10.

Next, the operation of this embodiment will be described with reference to FIG. First, the coherent X-rays 2 generated from the storage ring 1 are monochromatized to a desired wavelength λ1 (for example, 0.5 Å) by the crystal monochromators 3a and 3b. In other words, monochromatic X-rays having the same wavelength and phase can be obtained. Assuming that the angle between the crystal monochromator 3a and the incident X-ray 2 is θ and the crystal lattice spacing of (111) silicon constituting the crystal monochromator is d, the wavelength λ1 of the X-ray 4 from the crystal monochromator is λ1 = 2d sin θ. Therefore, by setting the incident angle of the incident X-ray 2 to an appropriate angle, the wavelength λ1 of the X-ray 4 from the crystal monochromator can be set to a desired value. X-rays 4 from the crystal monochromators 3a and 3b pass through the slits 5a and 5b,
Only the central portion of the line 4 is extracted, and the X-ray beam 6 has higher directivity and coherence.

The X-ray 6 obtained in this way is applied to the surface area of the sample 8 to be measured placed on the holder 7. Here, as shown in FIG. 2, a sample in which a first region 8a (refractive index n1) and a second region 8b (refractive index n2) are formed of different substances on a silicon substrate is defined as a sample 8 to be measured. Shall be used.

The angle between the surface of the sample 8 to be measured and the X-ray beam 6 (in other words, the mounting surface of the holder 7 and the X-ray beam 6
Angle) is adjusted to a desired angle by a goniometer, so that the unevenness on the surface of the first region 8a of the sample 8 to be measured or the unevenness at the interface between the first region 8a and the second region 8b is adjusted. Can be measured. That is, as shown in FIG. 2, when measuring the unevenness of the surface of the first region 8a, the angle between the X-ray beam and the surface of the first region 8a (the mounting surface of the holder and the X-ray beam The angle of the viewing angle is adjusted so that the angle formed by the first region 8a is close to the total reflection condition of the first region 8a. When measuring the unevenness of the interface between the first region 8a and the second region 8b, the X-ray beam is applied to the first region 8a.
a and the angle between the X-ray beam and the interface between the first region 8a and the second region 8b (the angle between the mounting surface of the holder and the X-ray beam) is equal to the entire angle of the second region 8b. The viewing angle is adjusted so that the angle is close to the reflection condition.

The range irradiated by the X-rays on the surface of the sample 8 to be measured is determined by the beam shape and the size of the X-rays and the viewing angle, but since the viewing angle is generally several degrees or less. , A vertically long range is irradiated with X-rays.

Thus, the X-rays 9 scattered and reflected on the surface area of the sample 8 to be measured are irradiated onto the recording medium 10,
A scattered image reflecting the X-ray coherence based on the unevenness is formed. Therefore, even if there is a composition variation in the measurement target area,
A scatter image distinct from the composition variation will be recorded.
When an imaging plate is used as the recording medium 10, the scattered image is read by a reader. When an X-ray film is used as the recording medium 10, the scattered image is developed, and the degree of blackening is read by a microdensitometer.

In this manner, the intensity distribution of the scattered image corresponding to the unevenness in the range irradiated with the X-rays 6 on the surface of the sample 8 to be measured is obtained. FIG. 3 shows an example of the scattering intensity distribution on the recording medium 10 (the intensity distribution in the longitudinal direction of the vertically long range irradiated by the X-ray 6).

After obtaining the scattering intensity distribution by the X-rays of the wavelength λ1, the angles of the crystal monochromators 3a and 3b are adjusted to select the X-rays of the wavelength λ2 (for example, 0.7 Å). The scattering intensity distribution by the X-ray of the wavelength λ2 is obtained by the same procedure as above. At this time, the holder 7
Of the mounting surface (viewing angle) is the same as in the case of the wavelength λ1. The scattering intensity distribution obtained by the irradiation of the X-ray of the wavelength λ2 is slightly different from the scattering intensity distribution obtained by the X-ray of the wavelength λ1.

As described above, the scattering intensity distribution by the X-ray of the wavelength λ1 and the scattering intensity distribution by the X-ray of the wavelength λ2 are obtained. Calculation means 1 calculates the correlation between these two scattering intensity distributions
As shown in FIG. 4, the unevenness of the surface area of the sample 8 to be measured (the unevenness of the surface of the first area 8a, or the unevenness of the interface between the first area 8a and the second area 8b) is obtained as shown in FIG. Can be measured.

When determining the unevenness of the interface, if the sample surface has unevenness, the phase of the X-rays reaching the interface may be shifted due to the unevenness, so that it is difficult to accurately measure the unevenness of the interface. Therefore, in such a case, it is preferable to obtain the interface unevenness using the surface unevenness information measured in advance.

In the above embodiment, the sample is irradiated with X-rays having different wavelengths at the same oblique angle. However, X-rays having the same wavelength may be irradiated at different oblique angles. By using the above method, even if there is a composition variation near the sample surface or the interface, it is possible to selectively measure the unevenness of the surface or the interface in distinction from the composition variation.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.
In the above embodiment, two regions (first and second regions) are assumed as regions having different refractive indices. However, the present invention can be similarly applied to three or more regions. In addition, while the unevenness of the sample surface or interface is determined by the method of the present invention, if the unevenness and the composition fluctuation are integrally measured using X-rays having different wavelengths and phases as described in the related art, It is also possible to measure composition variations. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0021]

According to the present invention, it is possible to accurately measure minute irregularities on a surface or an interface, distinguished from the composition variation, even if there is a composition variation near a sample surface or an interface serving as a measurement target area. Become.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a surface / interface roughness measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an X-ray reflection state on a sample to be measured.

FIG. 3 is a diagram illustrating an example of a scattering intensity distribution on a recording medium.

FIG. 4 is a view showing an example of unevenness of a sample to be measured obtained based on a scattering intensity distribution on a recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Storage ring 2, 4, 6, 9 ... X-ray 3a, 3b ... Crystal monochromator 5a, 5b ... Slit 7 ... Holder 8 ... Sample to be measured 10 ... Recording medium 11 ... Calculation means

Claims (2)

[Claims] An X-ray having coherence is monochromated, and monochromatic X-rays having different wavelengths are selectively reflected at an interface between regions having different refractive indices in the surface or thickness direction of a sample to be measured. The oblique angle is adjusted to irradiate at the same oblique angle, and the images obtained by the X-rays of each wavelength reflected by the sample to be measured are respectively recorded in the recording means, and the respective wavelengths recorded in the recording means are recorded. A method for measuring surface / interface roughness, comprising determining unevenness of a surface or an interface of the sample to be measured from a correlation between images corresponding to X-rays. 2. A wavelength selecting means for monochromaticizing an X-ray having coherence to select a desired wavelength, and irradiating the sample to be measured with the X-ray having the wavelength selected by the wavelength selecting means at a desired viewing angle. Oblique angle adjusting means for irradiating the sample to be measured with the oblique angle adjusted by the oblique angle adjusting means, and selectively at the interface between the surfaces of the sample to be measured or regions having different refractive indexes in the thickness direction. Recording means for recording an image obtained by X-rays reflected on the recording means, and means for determining the unevenness of the surface or interface of the sample to be measured from the correlation of each image corresponding to X-rays of different wavelengths recorded on the recording means. A surface / interface roughness measuring device characterized by having: