JP2010230481A - Sample analyzer and sample analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample analyzer allowing to align a coherent X-ray with a sample in a short time. <P>SOLUTION: When an X-ray optical axis and a sample 1 are aligned, an X-ray with a wavelength longer than that during measuring the sample is extracted and irradiated from coherent X-rays or X-rays with an optical axis identical with that of coherent X-rays by a spectrometer 11, X-rays irradiated to outside of an irradiation position are absorbed by a sample support portion 14 which includes an aperture 14h at the irradiation position of X-rays for the sample of an analysis object and to which an X-ray absorption layer 14c for absorbing X-rays irradiated to outside of the irradiation position is formed, and a transmissive X-ray intensity of X-rays irradiated to the sample 1 supported by the sample support portion 14 is detected by the detector 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sample analyzer and a sample analysis method for analyzing a sample using X-rays.

  Various thin films are used for electronic devices or magnetic devices typified by semiconductor MOS (Metal Oxide Semiconductor) devices. Thin film uniformity (film thickness, density, surface interface roughness, film stress, magnetization distribution, etc.) and device performance and reliability are closely related, and it is important to analyze these in detail to improve device performance. It is an important element for realizing high reliability.

  As a thin film evaluation method, there were a reflectance method using X-ray reflection and a small angle scattering method using X-ray scattering. Further, as a method for observing a minute portion on the surface, there are surface analysis methods such as SEM (Scanning Electron Microscope) and AFM (Atomic Force Microscope).

JP 2000-35408 A JP-A-61-116380

  In recent years, development of material analysis methods using coherent X-rays (hereinafter referred to as coherent X-rays) having substantially the same phase has been progressing. For example, the present inventor has proposed a method for irradiating a sample with coherent X-rays and analyzing a speckle pattern (intensity distribution) of scattered X-rays as a means for evaluating the uniformity of the structure of the sample (special feature). (See application 2007-283057.)

  Here, when adjusting the position of the coherent X-ray to the sample before measurement, the position of the sample or collimator is moved by the position adjustment mechanism, and the scattered X-ray intensity appearing in the forward scattering region or the crystal Bragg diffraction region. From this variation, a method for determining the position of the sample is used.

  However, when the sample becomes fine, the signal change is extremely small, and in order to detect this change in signal intensity, signal accumulation for a long time is necessary, and as a result, it takes time for alignment. there were.

  In view of the above points, an object of the present invention is to provide a sample analyzer and a sample analysis method capable of aligning coherent X-rays with a sample in a short time.

In order to achieve the above object, the following sample analyzer is provided.
In this sample analyzer, when aligning the X-ray optical axis with the sample, the coherent X-ray or the X-ray having the optical axis matched with the optical axis of the coherent X-ray is used. A spectrometer that extracts and irradiates long wavelength X-rays, and an X-ray absorption that has an opening at the X-ray irradiation position on the sample to be analyzed and absorbs the X-rays irradiated outside the irradiation position A sample holding unit on which a layer is formed, and a detector that detects the transmitted X-ray intensity of the X-rays irradiated on the sample held by the sample holding unit.

Moreover, the following sample analysis methods are provided.
In this sample analysis method, when the X-ray optical axis and the sample are aligned, the sample is obtained from the coherent X-ray or the X-ray having the optical axis matched with the optical axis of the coherent X-ray by a spectroscope. X-rays extracted and irradiated with X-rays having a longer wavelength than at the time of measurement, and having an opening at the X-ray irradiation position on the sample to be analyzed and absorbing the X-rays irradiated outside the irradiation position The X-ray irradiated to the outside of the irradiation position is absorbed by the sample holding part on which the absorption layer is formed, and the X-ray transmitted X-rays irradiated to the sample held on the sample holding part by the detector Intensity is detected, the alignment is performed according to the transmitted X-ray intensity, and the sample is irradiated with X-rays having a shorter wavelength than that during the alignment, and measurement is performed by the detector.

  According to the disclosed sample analyzer and sample analysis method, the coherent X-ray can be aligned with the sample in a short time.

It is a figure which shows the structure of the sample analyzer of this Embodiment. It is the perspective view which showed the positional relationship of the principal part of a sample analyzer. It is a figure which shows the structure of the surface opposite to the sample holding surface of a sample holding part. It is a figure which shows the relationship between the X-ray energy and attenuation | damping length in the X-ray absorption layer using Au. It is the figure which showed an example of the result of having adjusted the position of the sample holding part which hold | maintained the sample, and having measured the transmission X-ray intensity with respect to the coherent X-ray of a different wavelength. It is a figure which shows the structure of the sample analyzer which performs a X-ray holography measurement. It is a figure which shows the structure of the surface opposite to the sample holding surface of a sample holding part. It is a figure which shows the structure of the sample analyzer which performs two types of measurements.

Embodiments of a sample analyzer of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of the sample analyzer of the present embodiment.
FIG. 2 is a perspective view showing the positional relationship of the main parts of the sample analyzer.

  The sample analyzer analyzes a sample 1 and includes an X-ray source 10, a spectroscope (monochromator) 11, a slit 12, a collimator 13, a sample holding unit 14, a detector 15, a control unit 16, and a position adjustment unit 17. , 18.

  The X-ray source 10 collimates, for example, X-rays from an X-ray tube, X-rays from a rotating counter-cathode, radiated light, and the like as a coherent X-ray by a minute pinhole. Further, the X-ray source 10 may generate a short wavelength laser or a free electron laser in the above wavelength region and irradiate it as coherent X-rays.

  The spectroscope 11 extracts X-rays having a specific wavelength from coherent X-rays with energy distribution irradiated from the X-ray source 10. In the sample analyzer of the present embodiment, the spectroscope 11 extracts X-rays having a wavelength λ1 longer than that at the time of sample measurement from the X-ray source 10 when the X-ray optical axis and the sample 1 are aligned. At the time of sample measurement, a coherent X-ray with a wavelength λ2 for measurement is extracted from the coherent X-ray. The reason for extracting the X-ray having the wavelength λ1 longer than the wavelength λ2 at the time of measuring the sample will be described later.

  The slit 12 shapes coherent X-rays having a wavelength extracted by the spectroscope 11. The slit 12 is made of tantalum (Ta), molybdenum (Mo), or stainless steel (SUS) having a thickness of about 1 mm in order to prevent X-rays from passing through the portion other than the opening 12h. The diameter of the opening 12h is, for example, about 10 to 20 μm according to the type of coherent X-ray. For example, when using a short wavelength laser or a free electron laser, the aperture is narrowed.

  The collimator 13 focuses the coherent X-ray with respect to the sample 1. The collimator 13 is made of tantalum, molybdenum, or stainless steel having a thickness of about 500 μm, for example, so as not to allow X-rays to pass through the portion other than the opening 13h. The aperture 13h has a diameter of about 10 to 20 μm, for example, depending on the type of coherent X-ray.

The sample holder 14 includes a support frame 14a, a membrane 14b, and an X-ray absorption layer 14c.
The support frame 14a is, for example, silicon (Si) or the like, and supports the membrane 14b.

  The membrane 14b is, for example, a silicon nitride film (SiN) or the like and transmits coherent X-rays. For example, a minute sample 1 having a size of several μm or less is held on one surface (hereinafter referred to as a sample holding surface) of the membrane 14b.

FIG. 3 is a diagram illustrating the configuration of the surface of the sample holder opposite to the sample holding surface.
For example, a gold (Au) layer or a platinum (Pt) layer is used for the X-ray absorption layer 14c because of its high ability to absorb coherent X-rays and good adhesion to the membrane 14b. The X-ray absorption layer 14c is formed on the surface opposite to the sample holding surface of the membrane 14b. Furthermore, the X-ray absorption layer 14c has an opening 14h at the position where the sample 1 is irradiated with coherent X-rays, and the membrane 14b is exposed.

  The detector 15 detects the transmitted X-ray intensity of the coherent X-ray irradiated on the sample 1 held by the sample holding unit 14. For example, a CCD (Charge Coupled Device) detector or a scintillation detector is used as the detector 15.

  The control unit 16 is, for example, a computer and controls each unit of the sample analyzer. The control unit 16 may be a computer that analyzes the shape, stress, magnetization distribution, and the like of the sample 1 from the speckle pattern detected by the detector 15.

The position adjusting unit 17 moves the slit 12 in two axial directions (x1, y1 in FIG. 2) perpendicular to the X-ray optical axis to adjust the position of the opening 12h.
The position adjustment unit 18 moves the collimator 13 in two axial directions (x2, y2 in FIG. 2) perpendicular to the X-ray optical axis to adjust the position. In addition, the position adjusting unit 18 moves the sample holding unit 14 in a biaxial direction (x3, y3 in FIG. 2) perpendicular to the X-ray optical axis independently of the collimator 13 to adjust the position. The position adjusting unit 18 has a function of moving the collimator 13 in the x2 and y2 directions in FIG.

By the way, the wavelengths λ1 and λ2 of the coherent X-ray selected by the spectroscope 11 are determined in consideration of the following.
FIG. 4 is a diagram showing the relationship between X-ray energy and attenuation length in an X-ray absorption layer using Au. The horizontal axis represents X-ray energy (keV), and the horizontal axis represents the attenuation length (μm).

As the X-ray energy increases, the attenuation length increases.
The intensity of the transmitted X-ray is obtained by T = I ₀ exp (−x / Λ). Here, I ₀ is the intensity of the incident X-ray, x is the film thickness, and Λ is the attenuation length.

  When the thickness x of the X-ray absorbing layer 14c using Au is 1.5 μm, when the X-ray energy is 4 keV (wavelength λ1 = 3.1Å), Λ = 0.44 μm from the relationship of FIG. exp (−x / Λ) = 0.033. On the other hand, when x = 1.5 μm and the X-ray energy is 10 keV (wavelength λ2 = 1.24Å), Λ = 4.5 μm, so exp (−x / Λ) = 0.72.

That is, when the incident X-ray intensity I ₀ is constant, the transmitted X-ray intensity becomes 1/22 when the X-ray energy is lowered from 10 keV to 4 keV.
Therefore, when the X-ray optical axis and the sample 1 are aligned, if a coherent X-ray having a wavelength longer than the measurement wavelength is used, the coherent X-ray is easily absorbed by the X-ray absorption layer 14c, and is passed through the opening 14h. Only the X-ray intensity transmitted through the sample 1 remains, and the other transmitted X-rays are strongly attenuated. Thereby, the position of the sample 1 is easily detected by the detector 15.

  FIG. 5 is a diagram illustrating an example of a result of measuring the transmitted X-ray intensity with respect to coherent X-rays having different wavelengths by adjusting the position of the sample holder that holds the sample. The horizontal axis is the position X (μm), and the vertical axis is the transmitted X-ray intensity I (counts / sec).

  As shown in the figure, when the wavelength of the coherent X-ray is as short as λ2 = 1.24, the transmitted X-ray intensity is high at a portion other than the sample 1 portion and is about I = 200 counts / sec. Further, since the variation in transmitted X-ray intensity in the portion other than the sample 1 portion is √I, the variation is large, and the transmitted X-ray intensity from the sample 1 (about 20 counts / sec) is difficult to detect. Therefore, in order to perform alignment, it is necessary to increase the counting integration time and improve the statistical accuracy, which takes time.

  On the other hand, when the wavelength of the coherent X-ray is as long as λ1 = 3.1Å, as described above, the X-ray absorption effect by the X-ray absorption layer 14c is about 20 times higher than that in the case of λ2 = 1.24Å. Except for the sample 1 portion, the transmitted X-ray intensity is as low as about 10 counts / sec. Therefore, since the transmitted X-ray intensity from the sample 1 portion can be clearly determined, the X-ray optical axis can be aligned with the sample 1 efficiently in a short time.

From the above, the spectroscope 11 extracts coherent X-rays having a longer wavelength than that during sample measurement when aligning the X-ray optical axis with the sample 1.
In addition, the sample holding | maintenance part 14 is formed as follows, for example.

  First, the membrane 14b is formed on the surface of the silicon substrate by, for example, nitriding the silicon substrate, and the central silicon substrate is removed on the opposite surface of the sample holding surface. As a result, only the membrane 14b remains in the central portion, and a support frame 14a made of a silicon substrate is formed around the periphery. Thereafter, an X-ray absorption layer 14c is formed on the membrane 14b opposite to the sample holding surface.

  Note that the thickness x of the X-ray absorption layer 14c is desirable because the X-ray absorption capability increases as the thickness increases. However, the thickness x is determined according to the fine processing performance by FIB (Focused Ion Beam) or the like, the resistance of the membrane 14b, and the like.

  For example, when the membrane 14b using SiN is formed with a thickness of about 0.2 μm, the thickness x of the X-ray absorption layer 14c using Au is set to 1. to prevent the membrane 14b from being broken. The thickness is about 5 μm or less.

  The opening 14h of the X-ray absorption layer 14c is formed by FIB or the like. When forming the opening 14h by FIB, for example, when the thickness x of the X-ray absorption layer 14c is 1.5 μm so that the aspect ratio is 1: 1, a wide area of 1.5 × 1.5 μm is used. It will be formed.

Next, the operation of the sample analyzer shown in FIGS. 1 and 2 will be described.
First, the position adjustment between the X-ray optical axis and the sample 1 is performed.
The spectroscope 11 extracts and emits long-wavelength coherent X-rays from the coherent X-rays irradiated from the X-ray source 10 under the control of the control unit 16. For example, the spectroscope 11 extracts the above-described coherent X-ray of λ1 = 3.1３.

  Next, under the control of the control unit 16, the position adjustment unit 17 moves the slit 12 in the x1 and y1 directions so that the opening 12h is maximized so that the X-ray intensity detected by the detector 15 becomes maximum. Align with the X-ray optical axis. The collimator 13 and the sample 1 are removed from the X-ray optical axis by the position adjusting unit 18. Since the incident coherent X-ray is completely absorbed except for the opening 12h of the slit 12, the position adjustment is easy.

  Next, the position adjustment unit 18 under the control of the control unit 16 puts the collimator 13 into the X-ray optical axis, adjusts the position of the collimator 13 in the x2 and y2 directions, and detects the X-ray intensity detected by the detector 15. The opening 13h is aligned with the X-ray optical axis so that is maximized. Since the incident coherent X-ray is completely absorbed except for the opening 13h of the collimator 13, the position adjustment is easy.

  Next, under the control of the control unit 16, the position adjusting unit 18 puts the sample 1 and the sample holding unit 14 on the X-ray optical axis, and adjusts the position of the sample holding unit 14 in the x3 and y3 directions. As shown in FIG. 5, most of the long-wavelength coherent X-rays are absorbed by the X-ray absorption layer 14c except for the opening 14h. Therefore, the position where the transmitted X-ray intensity is maximum with the detector 15, that is, the position of the sample 1 can be easily detected.

  After adjusting the position of the X-ray optical axis and the sample 1 using the long-wavelength coherent X-ray in this way, the spectrometer 11 is controlled by the control unit 16 from the X-ray source 10. A coherent X-ray having a measurement wavelength λ2 is extracted from the irradiated coherent X-ray and irradiated. For example, the above-described coherent X-ray with λ2 = 1.24Å is extracted.

  When the wavelength is changed, the X-ray optical axis is slightly tilted. Therefore, the position adjusting unit 18 two-dimensionally scans the collimator 13 and the sample holding unit 14 together on the x2 and y2 axes, and determines the position where the transmitted X-ray intensity detected by the detector 15 is maximum. Find and fix. Since the slit 12 is close to the X-ray source 10 and has little influence on the wavelength change, it is not particularly necessary to adjust the position with respect to the X-ray optical axis. Thereby, the alignment of the X-ray optical axis of the coherent X-ray with the wavelength λ2 and the sample 1 is completed.

Thereafter, the detector 15 performs measurement of, for example, small-angle scattering speckles, and the control unit 16 performs analysis based on the measurement result, for example.
As described above, according to the sample analyzer of the present embodiment, when aligning the X-ray optical axis and the sample 1, the sample 1 is irradiated with coherent X-rays having a longer wavelength than that during sample measurement. Except for the coherent X-rays to be irradiated, they are absorbed by the X-ray absorption layer 14c provided in the sample holder 14. Thereby, the detector 15 can easily determine the position of the sample 1 and can efficiently align the coherent X-rays with the sample.

Note that the sample analyzer of this embodiment can also be applied to X-ray holography measurement.
FIG. 6 is a diagram illustrating a configuration of a sample analyzer that performs X-ray holography measurement.

The same components as those shown in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
The collimator 13 has an opening 13hx for passing the reference X-ray, in addition to the opening 13h for irradiating the sample 1 with coherent X-rays. In the sample holder 14, the X-ray absorption layer 14c also has an opening 14hx for allowing reference X-rays to pass.

FIG. 7 is a diagram illustrating the configuration of the surface of the sample holder opposite to the sample holding surface.
The X-ray absorption layer 14c has an opening 14hx for passing the reference X-ray in addition to the opening 14h provided at the position where the sample 1 is irradiated with the coherent X-ray, and exposes the membrane 14b. Yes. When the size of the opening 14h is 1.5 μm, the size of the reference X-ray opening 14hx is, for example, about 0.2 μm.

The opening 14hx may be formed so as to penetrate the membrane 14b. The opening 14hx can be formed by FIB.
The distance h between the opening 14h and the opening 14hx is set so as to satisfy the coherence length for generating interference.

The coherence length can be expressed by ξ _T = λ / 2 (L / d). Here, λ is the wavelength of the X-ray, L is the distance from the slit 12 to the sample 1, and d is the size of the opening 12h of the slit 12.
For example, when λ = 1.24 mm, L = 1 m, and d = 10 μm, ξ _T = 6.2 μm. Therefore, the distance h between the opening 14h and the opening 14hx may be 6.2 μm or less.

  In the sample analyzer as shown in FIG. 6, when the X-ray optical axis and the sample 1 are aligned, the sample 1 is passed through the large opening 14h as in the sample analyzer having the configuration shown in FIG. Is performed using coherent X-rays.

By using such a sample analyzer, X-ray holography measurement can be performed.
In the X-ray holography measurement, after alignment, the spectroscope 11 emits a coherent X-ray having a wavelength λ2 for measurement and comes out through the coherent X-ray irradiated to the sample 1 and the opening 14hx. Interference with reference X-rays. Thereby, X-ray holography is measured by the detector 15.

Note that the sample analyzer may measure crystal diffraction speckles in addition to small-angle scattering speckles.
FIG. 8 is a diagram illustrating a configuration of a sample analyzer that performs two types of measurements.

The same components as those shown in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
This sample analyzer has two detectors 15a and 15b. The detector 15a measures small-angle scattering speckles, and the detector 15b measures crystal diffraction speckles.

  By performing both measurements, the sample can be analyzed in more detail. When aligning the X-ray optical axis with the sample 1, the detector 15a may be used, but the detector 15b is used to perform alignment based on the transmitted X-ray intensity appearing in the crystal Bragg diffraction region. May be.

  In addition, after the alignment of the X-ray optical axis and the sample 1 without using the detector 15b, the detector 15a is moved to the position of the detector 15b by a driving mechanism (not shown) to measure crystal diffraction speckles. May be.

As mentioned above, although one viewpoint of the sample analyzer and sample analysis method of this invention was demonstrated based on embodiment, these are only examples and are not limited to said description.
For example, in the above description, the X-ray having the wavelength λ1 for sample position adjustment has been described as being extracted from the coherent X-ray irradiated from the X-ray source 10 that is also used when the spectroscope 11 performs sample measurement. It is not limited. In addition to the X-ray source 10, the same alignment can be achieved by using an X-ray source that irradiates X-rays having a long wavelength exclusively for position adjustment, adjusted so that the optical axis coincides with the coherent X-ray for measurement. Is possible.

DESCRIPTION OF SYMBOLS 1 Sample 10 X-ray source 11 Spectrometer 12 Slit 12h, 13h, 14h Opening part 13 Collimator 14 Sample holding part 14a Support frame 14b Membrane 14c X-ray absorption layer 15 Detector 16 Control part 17, 18 Position adjustment part

Claims (5)

When aligning the X-ray optical axis with the sample, from the coherent X-ray or the X-ray having the optical axis aligned with the optical axis of the coherent X-ray, X-rays having a longer wavelength than that at the time of sample measurement A spectroscope to extract and irradiate;
A sample holder having an X-ray absorption layer that has an opening at the X-ray irradiation position on the sample to be analyzed and absorbs the X-ray irradiated outside the irradiation position;
A detector for detecting the transmitted X-ray intensity of the X-rays applied to the sample held by the sample holding unit;
A sample analyzer characterized by comprising: A collimator for focusing the X-rays irradiated on the sample;
After the alignment between the X-ray optical axis and the sample, the wavelength of the X-ray is changed to the wavelength at the time of sample measurement by the spectroscope, and the sample holder and the collimator are moved together to be changed. A position adjusting unit for aligning the wavelength with the X-ray optical axis;
The sample analyzer according to claim 1, comprising:   The sample analyzer according to claim 1, wherein the X-ray absorption layer has another opening for passing a reference X-ray for X-ray holography measurement. When aligning the X-ray optical axis with the sample, a wavelength longer than that at the time of sample measurement is obtained from the coherent X-ray or the X-ray having the optical axis matched with the optical axis of the coherent X-ray by a spectrometer. X-ray extracted and irradiated,
The sample holding portion formed with an X-ray absorption layer that has an opening at the X-ray irradiation position on the sample to be analyzed and absorbs the X-rays irradiated outside the irradiation position. Absorbs the irradiated X-rays,
The detector detects the transmitted X-ray intensity of the X-ray irradiated to the sample held in the sample holding unit,
Perform the alignment according to the transmitted X-ray intensity,
A sample analysis method comprising: irradiating the sample with X-rays having a shorter wavelength than that at the time of alignment and performing measurement by the detector.   5. The sample analysis method according to claim 4, wherein at the time of measuring the sample, a reference X-ray and the X-ray are caused to interfere with each other, and X-ray holography is measured by the detector.

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