JP5347461B2 - Sample analyzer and sample analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample analyzer capable of evaluating local uniformity of a sample surface or an interface, by converting simply an X-ray intensity distribution into an actual image. <P>SOLUTION: A sample 2 which is a measuring object and an X-ray reflecting mirror 3 are irradiated with an interfering X-ray, and a control part 7 controls an incident angle or an incident position to the X-ray of the sample 2 or the X-ray reflecting mirror 3 so that a first reflected X-ray from the sample and a second reflected X-ray from the X-ray reflecting mirror 3 are overlapped together. Then, the X-ray intensity distribution by interference between the overlapped first reflected X-ray and second reflected X-ray is detected by a detection part 8, and an operation processing part 9 converts the X-ray intensity distribution into actual space data. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a sample analyzer and a sample analysis method, and more particularly 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. Analyzing these in detail improves device performance. It is an important element for realizing high reliability.

Thin film evaluation methods include a reflectance method using X-ray reflection and a small-angle scattering method using X-ray scattering, and it is possible to analyze the average film thickness, density, and unevenness of a portion irradiated with X-rays. It was. As a method for observing surface uniformity, there are surface analysis methods such as SEM (Scanning Electron Microscope) and AFM (Atomic Force Microscope).
JP 2000-35408 A JP-A-61-116380

  However, the reflectance method and the small angle scattering method cannot analyze the local uniformity within the X-ray irradiation surface, and the SEM and AFM cannot evaluate the uniformity inside the sample such as the interface. .

  As a means for evaluating the homogeneity of the structure of the sample, the inventor irradiates the sample with coherent X-rays (hereinafter referred to as coherent X-rays) having substantially the same phase, and a speckle pattern (intensity distribution) of scattered X-rays. ) Has been proposed (Japanese Patent Application No. 2007-283057).

  However, when trying to convert the intensity distribution of scattered X-rays into a real image (real space data) for evaluating the surface irregularities of the sample, information on the phase is lost, so that the phase is restored. A long and repeated calculation is required.

  In view of the above points, the present inventor has developed a sample analysis apparatus and a sample analysis method that can easily convert the X-ray intensity distribution into a real image and evaluate local uniformity of the surface and interface of the sample. The purpose is to provide.

  In order to achieve the above object, a sample analyzer having the following configuration is provided. The sample analyzer includes an X-ray reflection mirror, an X-ray irradiation unit that irradiates the sample and the X-ray reflection mirror with coherent X-rays, a first reflected X-ray from the sample, and the X-ray reflection A control unit that controls an incident angle or an incident position of the sample or the X-ray reflecting mirror with respect to the X-ray so that the second reflected X-ray from the mirror overlaps; and the overlapping first reflected X-ray; A detector that detects an X-ray intensity distribution due to interference with the second reflected X-ray; and an arithmetic processing unit that converts the X-ray intensity distribution into real space data.

  It is possible to easily convert the X-ray intensity distribution into a real image and evaluate the local uniformity of the surface and interface of the sample.

Hereinafter, the present embodiment will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing the configuration of the sample analyzer of the present embodiment.
The sample analyzer 1 includes an X-ray reflection mirror 3, an X-ray irradiation unit 4, incident angle / incident position adjustment units 5 and 6, a control unit 7, a detection unit 8, and an arithmetic processing unit 9 that are juxtaposed to a sample 2 to be measured. And a vacuum chamber 10 and a collimator 11.

FIG. 2 is a cross-sectional view showing an example of a sample.
The sample 2 is, for example, a semiconductor substrate 2a and a thin film 2b such as a SiO ₂ (silicon oxide) film formed on the semiconductor substrate 2a. Further, the sample 2 may have a multilayer structure in which a plurality of thin films 2b are stacked. The sample analyzer 1 of the present embodiment analyzes the surface and interface of the thin film 2b of such a sample 2.

FIG. 3 is a perspective view showing an example of the X-ray reflecting mirror.
In the sample analyzer 1 of the present embodiment, the X-ray reflection mirror 3 has, for example, a shape that surrounds the sample 2 so as to have an opening 3a at the center and expose the surface of the sample 2. . Further, the X-ray reflecting mirror 3 is used that has less irregularities than the surface of the sample 2. For example, mirror-polished Si (silicon) crystal is used.

  The X-ray irradiation unit 4 irradiates the sample 2 and the X-ray reflection mirror 3 with coherent X-rays. For example, the X-ray irradiation unit 4 collimates X-rays, radiated light, and the like from an X-ray tube whose wavelength is a soft X-ray or hard X-ray wavelength region, and irradiates it as a coherent X-ray. To do. Further, the X-ray irradiation unit 4 may generate a short wavelength laser or a free electron laser that is in the above wavelength region and irradiate it as coherent X-rays.

The incident angle / incident position adjusting units 5 and 6 are realized by, for example, a goniometer or a moving stage.
The incident angle / incident position adjustment unit 5 adjusts the angle and position of the sample 2 under the control of the control unit 7 to adjust the incident angle and the incident position of the coherent X-ray on the sample 2.

The incident angle / incident position adjustment unit 6 adjusts the angle and position of the X-ray reflection mirror 3 under the control of the control unit 7, and sets the incident angle and incident position of the coherent X-ray to the X-ray reflection mirror 3. adjust.
The control unit 7 controls the incident angle / incident position adjusting units 5 and 6 to adjust the incident angle or the incident position of the coherent X-ray to the sample 2 or the X-ray reflecting mirror 3, respectively. 3 so that the reflected X-rays from 3 overlap.

  The incident angle to the sample 2 is adjusted in consideration of analysis sensitivity. For example, when the sample 2 has a multilayer film structure, the reflection intensity from the surface or interface of a certain film is increased (or decreased) by changing the incident angle. Therefore, the incident angle is determined by simulation according to the structure of the sample 2 so that the reflection intensity from the surface or interface of the film whose analysis sensitivity is to be improved is increased.

  The detection unit 8 detects the intensity distribution of interference X-rays generated by overlapping the reflected X-rays from the sample 2 and the reflected X-rays from the X-ray reflecting mirror 3. The detection unit 8 is, for example, a zero-dimensional detector, a one-dimensional detector, or a two-dimensional detector, and is, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Further, a photodiode array, a position sensitive proportional coefficient tube (PSPC), an imaging plate, or the like may be used.

  Although not shown, the sample analyzer 1 has an adjustment mechanism that adjusts the position of the detection unit 8. For example, when a two-dimensional detector is used, the center of the interference X-ray is The position of the detection unit 8 is adjusted so as to be in the center of the detection surface.

The arithmetic processing unit 9 performs Fourier transform or inverse Fourier transform on the intensity distribution of the interference X-ray detected by the detection unit 8 to convert it into a real image of the measurement region of the sample 2.
The control unit 7 and the arithmetic processing unit 9 can be realized by one or a plurality of computers, for example.

  The vacuum chamber 10 covers an analysis region including the sample 2, the X-ray reflection mirror 3, and the detection unit 8, and prevents the X-ray interference from being lowered during the analysis of the sample 2 due to atmospheric fluctuations. Is provided. The inside of the vacuum chamber 10 is exhausted by an exhaust pump (not shown).

The collimator 11 shapes the size of the coherent X-ray to be irradiated.
Hereinafter, a sample analysis method using the sample analyzer 1 will be described.
First, the inside of the vacuum chamber 10 is exhausted to about 10E ^{−3 to} 10E ⁻⁸ Torr, for example, by an exhaust pump (not shown), and the X-ray irradiation unit 4 irradiates the sample 2 and the X-ray reflection mirror 3 with coherent X-rays. .

FIG. 4 is a diagram showing how the incident angle and the incident position of coherent X-rays are adjusted.
Only the sample 2, the X-ray reflecting mirror 3, the control unit, and the detection unit 8 are illustrated, and the other configurations are not illustrated.

  The sample 2 and the X-ray reflection mirror 3 are controlled by the control unit 7 of FIG. 1 so that the position in the Z-axis direction and the incident angles θ1 and θ2 with respect to the coherent X-rays 15a and 15b are controlled so that the reflected X-rays 16a and 16b overlap. Adjusted. The detection unit 8 is adjusted to a position of 2θ1 so that the interference X-ray can be detected efficiently.

  The X-ray irradiation unit 4 shown in FIG. 1 and the vacuum chamber 10 itself are adjusted in the X, Y, and Z axis directions, and the coherent X-rays 15 a and 15 b are irradiated to the sample 2 and the X-ray reflection mirror 3. In this way, alignment may be performed.

FIG. 5 is a diagram showing the state of interference by reflected X-rays when the incident angle θ1> θ2.
Below, the case where a two-dimensional detector is used as the detection part 8 is shown.

  When the incident angle θ1> θ2, the reflected X-rays 18a and 18b by the coherent X-rays 17a and 17b incident on the sample 2 are incident on the X-ray reflecting mirror 3 on the left side of the sample 2 in FIG. It overlaps with the reflected X-rays 18c and 18d by the coherent X-rays 17c and 17d. On the detection surface of the detector 8, interference X-rays are detected in a region 8 a where the reflected X-rays 18 a and 18 b from the sample 2 and the reflected X-rays 18 c and 18 d from the X-ray reflecting mirror 3 are incident. A region 8b on the outer periphery of the region 8a is a region where the reflected X-rays 18a and 18b from the sample 2 are not incident and is not used for analysis.

FIG. 6 is a diagram showing the state of interference by reflected X-rays when the incident angle θ1 <θ2.
When the incident angle θ1 <θ2, the reflected X-rays 20a and 20b by the coherent X-rays 19a and 19b incident on the sample 2 are incident on the X-ray reflecting mirror 3 on the right side of the sample 2 in FIG. It overlaps with the reflected X-rays 20c and 20d by the coherent X-rays 19c and 19d. On the detection surface of the detector 8, interference X-rays are detected in a region 8 c where the reflected X-rays 20 a and 20 b from the sample 2 and the reflected X-rays 20 c and 20 d from the X-ray reflecting mirror 3 are incident. The outer region 8d of the region 8c is a region where the reflected X-rays 20a and 20b are not incident from the sample 2 and is not used for analysis.

  In addition to adjusting the incident angles θ1 and θ2, the reflected X-ray from the sample 2 and the reflected X-ray from the X-ray reflecting mirror 3 can be adjusted by adjusting the tilt angle of the sample 2 with respect to the coherent X-ray. You may make it interfere.

FIG. 7 is a diagram showing a state of interference by reflected X-rays when the tilt angle φ ≠ 0 of the sample.
For example, when the sample 2 is tilted at an angle φ on the right side with respect to the incident direction of the coherent X-rays 21a, 21b, 21c, and 21d, the reflected X-rays 22a, 22b, 22c, and 22d are bent to the right. At this time, in FIG. 7, the reflected X-rays 22e, 22f by the coherent X-rays 21e, 21f irradiated to the X-ray reflecting mirror 3 on the right side of the sample 2 are reflected X-rays 22a, 22b, 22c, It overlaps with 22d and causes interference. Thereby, the interference X-ray is detected in the region 8e on the detection surface of the detection unit 8. A region 8f on the outer periphery of the region 8e is a region where no interference X-ray is detected, and is not used for analysis.

  As shown in FIGS. 5 to 7, in the sample analyzer 1 of the present embodiment, the X-ray reflecting mirror 3 having a shape surrounding the sample 2 is used, so that X-rays around the sample 2 are used. X-rays reflected by the reflection mirror 3 can be used, and adjustment to interfere with the reflected X-rays from the sample 2 is facilitated.

  5 to 7, the case where a two-dimensional detector is used as the detecting unit 8 has been described. However, the detection surface (particularly, the regions 8a, 8c, and 8e) of FIGS. Interference X-rays may be detected by scanning a dimension detector or a one-dimensional detector.

FIG. 8 is a diagram illustrating an example of the intensity distribution of the interference X-rays detected by the detection unit.
Here, the intensity distribution of the interference X-rays in the x-axis direction detected on the detection surface of the detection unit 8 shown in FIGS. The intensity distribution of the interference X-ray in the y-axis direction is also detected in the same manner.

The horizontal axis is the position (μm) in the x-axis direction, and the vertical axis is the detection intensity (au).
The intensity distribution obtained here is a hologram using the reflected X-ray from the X-ray reflecting mirror 3 as a reference wave.

  The arithmetic processing unit 9 acquires the intensity distribution of the interference X-ray detected by the detection unit 8, performs inverse Fourier transform on the intensity distribution, and converts it into real space data. For example, when analyzing the unevenness of the surface of the sample 2, if the detection intensity at the detection position (xd, yd) of the two-dimensional detector is I (xd, yd), the position (Xs, Ys) of the surface of the sample 2 The height Zs (Xs, Ys) at is Zs (Xs, Ys) = IFFT (I (xd, yd)).

  “IFFT” represents an inverse fast Fourier transform for the intensity I (xd, yd). Here, since the interference component is converted, the same result can be obtained by performing Fourier transform instead of inverse Fourier transform.

FIG. 9 is an example of the uneven distribution of the sample obtained by inverse Fourier transform.
The horizontal axis is the position Xs on the sample 2, and the vertical axis is the height Zs. In this way, by converting into real space data, it is possible to easily evaluate what unevenness is generated at which position.

When two-dimensional data is used, a two-dimensional distribution of unevenness is obtained by two-dimensional inverse Fourier transform.
Thus, in the sample analyzer 1 of the present embodiment, the reflected X-rays from the sample 2 and the reflected X-rays from the X-ray reflecting mirror 3 are overlapped and interfered, and the intensity distribution of the interference X-rays (hologram) ) Is detected. By performing inverse Fourier transform on this hologram, the surface and interface of the sample 2 can be evaluated easily by reproducing it into a real image without performing long-term repetitive calculations.

  In the above, the case where the uniformity of the surface of the sample 2 is evaluated without changing the external field has been described. However, the external field such as temperature, magnetic field, electric field or pressure is changed, and the sample 2 at that time is changed. You may make it analyze uniformity, such as the density of a surface or an interface.

FIG. 10 is a diagram illustrating a configuration of a sample analyzer that performs measurement by changing temperature, magnetic field, electric field, or pressure.
The same components as those of the sample analyzer 1 shown in FIG.

The sample analyzer 1a shown in FIG. 10 has an external field application unit 31 that applies heat, a magnetic field, an electric field, or pressure to the sample 2.
The external field application unit 31 is, for example, a He (helium) cryostat, a heater, a lamp, a permanent magnet, an electromagnet, a superconducting electromagnet, a high voltage power source, a pulse generator, and the like, and is controlled by the control unit 7.

The measurement performed by changing the temperature is performed, for example, in order to analyze the change of the crystal structure or the change of the ferroelectric domain of the ferroelectric.
The external field application unit 31 puts the inside of the vacuum chamber 10 into a low temperature state (for example, 4K) or a high temperature state (for example, 1300K) under the control of the control unit 7. At this time, the intensity distribution of the interference X-ray detected by the detection unit 8 is converted into a real image by, for example, inverse Fourier transform.

  As a result, it is possible to analyze the changes in the surface and interface irregularities of the sample 2 due to changes in the crystal structure and the ferroelectric domain due to temperature, variations in the ferroelectric domain, and the like with real images. That is, it is possible to analyze at which position of the sample 2 the ferroelectric domain is changed.

The measurement performed by changing the magnetic field is performed, for example, to analyze a change in the magnetic domain or a change in magnetism (Curie temperature, Neel temperature).
The external field application unit 31 applies, for example, a magnetic field of 0 to 10 Tesla to the sample 2 under the control of the control unit 7. At this time, by converting the intensity distribution of the interference X-rays detected by the detection unit 8 into a real image, it is possible to analyze at which position of the sample 2 the change of the magnetic domain and magnetism due to the magnetic field application occurs. .

The measurement performed by changing the voltage is performed, for example, to analyze the change of the ferroelectric domain of the ferroelectric.
The external field application unit 31 applies, for example, a voltage of ± 10 KV to the sample 2 under the control of the control unit 7. At this time, by converting the intensity distribution of the interference X-rays detected by the detection unit 8 into an actual image, it is possible to analyze at which position of the sample 2 the change of the ferroelectric domain due to voltage application occurs.

In addition, in order to apply stress to the sample 2 and examine the influence thereof, the intensity distribution of the detected interference X-ray may be converted into an actual image and analyzed.
As described above, the sample analysis apparatus and the sample analysis method of the present case have been described based on a plurality of embodiments, but these are merely examples and are not limited to the above description.

  For example, in the above description, the X-ray reflecting mirror 3 has a shape that surrounds the sample 2. However, a plurality of mirrors are arranged so as to surround the sample 2, and the incident angle is set respectively. Or the incident position may be adjustable. However, it is desirable that the coherent X-rays are arranged close to the sample 2 so that the sample 2 and the X-ray reflecting mirror 3 are simultaneously irradiated.

It is a figure which shows the structure of the sample analyzer of this Embodiment. It is sectional drawing which shows an example of a sample. It is a perspective view which shows an example of an X-ray reflective mirror. It is a figure which shows a mode that the incident angle and incident position of a coherent X-ray are adjusted. It is a figure which shows the mode of interference by reflected X-ray in the case of incident angle (theta) 1> (theta) 2. It is a figure which shows the mode of interference by reflected X-ray in the case of incident angle (theta) 1 <(theta) 2. It is a figure which shows the mode of interference by reflected X-rays when the tilt angle φ ≠ 0 of the sample. It is a figure which shows an example of the intensity distribution of the interference X-ray detected by the detection part. It is an example of the uneven | corrugated distribution of the sample obtained by the inverse Fourier transform. It is a figure which shows the structure of the sample analyzer which measures by changing temperature, a magnetic field, an electric field, or a pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample analyzer 2 Sample 3 X-ray reflection mirror 4 X-ray irradiation part 5,6 Incident angle / incident position adjustment part 7 Control part 8 Detection part 9 Arithmetic processing part 10 Vacuum chamber 11 Collimator

Claims (5)

An X-ray reflecting mirror having a shape surrounding the sample ;
And X-ray irradiation unit for irradiating the coherent X-ray to the sample and the X-ray reflecting mirror,
An incident angle or an incident position of the sample or the X-ray reflecting mirror with respect to the X-ray is set so that the first reflected X-ray from the sample and the second reflected X-ray from the X-ray reflecting mirror overlap each other. A control unit to control;
A detector that detects an X-ray intensity distribution due to interference between the first reflected X-ray and the second reflected X-ray,
An arithmetic processing unit for converting the X-ray intensity distribution into real space data;
A sample analyzer characterized by comprising: The sample analysis apparatus according to claim 1, wherein an analysis region including the sample, the X-ray reflection mirror, and the detection unit is covered with a vacuum chamber. The sample analyzer according to claim 1, further comprising an external field applying unit that applies heat, a magnetic field, an electric field, or pressure to the sample. The sample has one or a plurality of films, and the control unit controls the incident angle with respect to the sample so that the reflection intensity from the surface or interface of the film whose analysis sensitivity is desired to be increased. The sample analyzer according to any one of claims 1 to 3. Irradiate the sample and the X-ray reflecting mirror having a shape surrounding the sample with coherent X-rays,
  An incident angle or an incident position of the sample or the X-ray reflecting mirror with respect to the X-ray is set so that the first reflected X-ray from the sample and the second reflected X-ray from the X-ray reflecting mirror overlap each other. Control
  Detecting an X-ray intensity distribution due to interference between the first reflected X-ray and the second reflected X-ray,
  A sample analysis method, wherein the X-ray intensity distribution is converted into real space data.

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