JPH07110311A - Method and apparatus for surface analysis of sample - Google Patents

Abstract

PURPOSE:To provide a photoelectron spectrometry for analysis of physical and chemical quantities of minute areas, such as depthwise analysis, analysis of band structures, and analysis of crystal structures of component elements. CONSTITUTION:Light in a wavelength area from soft X rays to vacuum ultraviolet rays is condensed by an optical element 4 to irradiate a microscopic area of the surface of a sample 4 to measure kinematic energy of photoelectrons released therefrom with an energy analyzer 9, and at the same time, an angle distribution of the photoelectrons is measured by a position analysis type detector 10 as two-dimensional image. Thus, an analysis on the direction of depth of component elements, an analysis of band structures, an analysis of crystal structures and the like are accomplished in the microscopic area from photoelectron signals thus obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for analyzing a sample surface, and more particularly, it relates to an energy distribution and an angular distribution of photoelectrons emitted from a minute area of the sample surface on which light having a specific energy is collected. The present invention relates to a sample surface analysis method for analyzing a physical quantity or a chemical quantity related to a sample and an analyzer for the same.

[0002]

2. Description of the Related Art With the miniaturization and thinning of semiconductor elements, it is required to control the formation of various thin films in a minute area. For such control, measurement technology for the surface and interface states of various thin films is indispensable, and high-precision depth direction analysis technology for elements and chemical bonding states in minute regions,
There is a strong demand for analytical techniques for the band structure and crystal structure of a sample.

Conventionally, by photoelectron spectroscopy (called XPS when incident light is X-ray, UPS when incident light is vacuum ultraviolet),
There are many studies on non-destructive depth direction analysis of elements or their chemical states using the angular distribution of photoelectron signal intensity and band structure analysis by associating kinetic energy of photoelectrons with emission angles (Shizuo Miyake, Electron diffraction / electron spectroscopy, p357, 1991, Kyoritsu Shuppan). In addition, a crystal structure analysis (so-called photoelectron holography) by Fourier transforming the angular distribution of photoelectron signal intensity has been recently proposed (Burton, Journal of Electron Spectroscopy and Related Phenomena, 51, 37 ( 1990) .JJ Barton, Journal
of Electron Spectroscopy and Related Phenomena, 5
1 , p37 (1990)) and is expected as a new analytical method.

[0004]

However, in the surface analysis by measuring the angular distribution of the photoelectron signal intensity using the above-mentioned photoelectron spectroscopy, the light that excites the sample is irradiated onto the sample without being collected. The obtained depth direction distribution, band structure, crystal structure, etc. were average information in a wide range of centimeter to millimeter scale.
Therefore, it cannot be used for analysis of various thin films in microscopic and submicron scale minute regions such as in the semiconductor process.

Further, the angular distribution of photoelectron emission can be obtained by rotating an energy analyzer having a small solid angle of photoelectron uptake, which has been often used in the past, around the sample or by rotating the sample while fixing the energy analyzer. In the method of obtaining, it took a long time to measure the angular distribution for one measurement point, and measurement for many points on the sample was not realistic.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to determine the physical distribution and the stoichiometry of elements such as band distribution, crystal structure, etc. in the depth direction distribution in a minute region on the surface of a sample.
It is an object of the present invention to provide an analytical method and an analytical device for the simple analysis.

[0007]

In order to achieve this object, in the present invention, light in the wavelength range from soft X-rays to vacuum ultraviolet rays is focused on a minute area on the sample surface by an optical element. The kinetic energy of the photoelectrons emitted from the surface of the sample upon irradiation is measured at the same time using an energy analyzer capable of displaying the emission angle distribution of the photoelectrons as a two-dimensional image. At this time, the emission angle distribution of the photoelectrons is subjected to integral conversion to obtain the depth direction distribution of the specific element or its chemical state and the crystal structure, and the kinetic energy of the photoelectrons and the emission angle are correlated to obtain the band structure. Are measured respectively. The electrode structure of the energy analyzer used here has a shape of a part of two circular spheres or a part of an ellipsoid.

Further, by scanning the light condensing point on the sample surface, it is possible to measure the distribution of the physical quantity or the chemical quantity in a specific area range on the sample surface. Here, as a method of scanning the light condensing point on the sample surface, there are a method of moving the entire sample with respect to the fixed condensing point and an optical element for condensing the light on the fixed sample. There is a way to move.

The optical element for condensing the light may be of a reflective type, a diffractive type, or a refractive type, or a combination thereof may be used.

[0010]

In this sample surface analysis method and analyzer, light in the wavelength range from soft X-rays to vacuum ultraviolet rays is converted into a microbeam having a diameter on the order of microns or submicrons by an optical element. The size of the photoelectron generation region can be reduced to about the beam diameter. As this optical element, a reflective optical element such as a Walter type mirror or a Schwarzschild type mirror,
A diffractive optical element such as a zone plate, or other refractive optical element can be used.

As described above, in the present invention, by condensing light and limiting the photoelectron generation region to a minute region, the analysis of the angular distribution of the emitted photoelectrons shows that the element in the minute region or the chemical state Fracture depth direction analysis is possible. Further, the band structure analysis in a minute region can be performed by correlating the angular distribution of emitted photoelectrons with the kinetic energy. Furthermore, by performing a Fourier transform, which is a type of integral transform, on the angular distribution of the emitted photoelectrons,
It is also possible to analyze the crystal structure of a minute area.

Further, by scanning the light collecting point on the sample surface, the three-dimensional distribution of the element or its chemical state,
It is possible to map the distribution of a specific band structure or crystal structure on the sample surface.

On the other hand, according to the present invention, as an energy analyzer for measuring the angular distribution of photoelectrons having a specific kinetic energy emitted from a minute area, the angular distribution of photoelectrons can be obtained at one time as a two-dimensional image. Uses an energy analyzer. In this energy analyzer, the electrode structure is part of an ellipsoidal sphere (Eastman, Donnelon, Hahn, Himsel: Nuclear Instruments and Methods, 172: 327 (1980).
JJDonelon, NCHien, FJHimpsel: Nuclear Inst
ruments and Methods 172, p327 (1980)), or a part of a sphere (Daimon, Journal of the Crystallography Society of Japan, 31: 155 (1989)). The emitted photoelectrons are reflected and the angular distribution is projected as a two-dimensional image on the position-resolved detector. By using such an energy analyzer, the angle distribution measurement time can be significantly shortened. Furthermore, a mechanism for inclining the measurement sample or rotating the energy analyzer around the sample is unnecessary, and the device configuration can be simplified.

[0014]

【Example】

(Embodiment 1) FIG. 1 shows an example of the structure of an analyzer for measuring the angular distribution of the signal intensity of photoelectrons from a minute region using a microbeam of soft X-rays or vacuum ultraviolet rays.

Both the optical system and the photoelectron detection system are installed in an ultrahigh vacuum. In the figure, the elements installed in the ultra-high vacuum are surrounded by broken lines. Soft X emitted from light source 1
The light in the wavelength region from the line to the vacuum ultraviolet ray is monochromaticized into light having a predetermined energy by the spectroscope 2, and is condensed on the surface of the sample 4 using the optical element 3. The spectroscope 2 is controlled by the controller 5, and the sample 4 is installed on the sample table 7. The sample table 7 is connected to the moving mechanism 6 installed outside the vacuum and controlled by the controller 8 so that the sample table 7 can be moved from outside the vacuum.

The photoelectrons emitted from the sample 4 are inverted by the electric field generated by the electrode 9 and detected by the position-resolved detector 10. In this case, the shape of the electrode 9 is a part of a sphere or a part of an ellipsoid so that the angular distribution of the photoelectrons emitted from the sample 4 is projected on the position detector 10.

In order to measure the angular distribution of the emitted photoelectrons from the minute area, first, the sample table 7 is operated by the moving mechanism 6 to move the analysis point on the sample surface to the focus point of the optical element 3. An appropriate voltage is applied to the electrode 9 by the controller 11 so that only photoelectrons having a specific kinetic energy pass through the slit 12 in the preceding stage of the position-resolved detector 10. At this time, an auxiliary electrode other than the electrode 9 may be installed in an appropriate place so that photoelectrons having a kinetic energy other than the assumed kinetic energy are not mixed in as much as possible. Then, since the angular distribution of the emitted photoelectrons is projected on the position-resolved detector 10, the angle distribution on the position-resolved detector 10 is 2.
If the data of the dimensional photoelectron signal intensity is taken into the computer 13, the angular distribution can be obtained at once.

By analyzing the emission angle distribution of the photoelectrons thus obtained, the nondestructive depth direction analysis of the constituent elements or their chemical states in the microscopic region which is the focusing point on the sample 4 can be performed. By analyzing the angular distribution and kinetic energy, it is possible to analyze the band structure in the minute region, and further Fourier transform the above angle distribution to analyze the crystal structure in the minute region. , Can be performed by the computer 13,
Further, image processing can be performed as necessary and output to the display device 14.

In this embodiment, it is assumed that the computer 13, controls the controllers 8, 5 and 11.
If necessary, the control of the controllers 8, 5 and 11 and the processing of the obtained data may be performed by different computers.

If the above-mentioned measurement is repeated while scanning the focal point of the incident light on the sample surface by the moving mechanism 6, the depth distribution, band structure, crystal structure, etc. on the sample surface will be 2
The dimensional distribution can be obtained.

As described above, according to this embodiment, it is possible to measure the angular distribution of the emitted photoelectrons from the minute area in a short time, so that the minute area on the sample surface can be easily analyzed. .

(Example 2) In Example 1 described above, the sample stage 7 was moved independently of the energy analyzer. However, if the sample table 7 is made independently movable, the sample table 7 becomes large, and therefore it may not be possible to realize it due to the relationship with the size of the energy analyzer and problems in the device configuration. Therefore, in the second embodiment, the sample stage and the energy analyzer are integrated, and the sample 4 is directly installed on the support 15 of the electrode 9 of the energy analyzer (FIG. 2). In this figure, only a portion substantially different from that in FIG. 1 is drawn, and the support base 15 can be moved with respect to the focal point by the moving mechanism 17 controlled by the controller 16.

According to the second embodiment, the device structure around the energy analyzer can be made compact.

(Embodiment 3) With the construction of Embodiment 2, the apparatus construction around the energy analyzer can be made compact, but it is difficult to exchange the sample. In the third embodiment shown in FIG. 3, in order to facilitate sample exchange, the optical element 3 and the energy analyzer are integrated so as not to form a complicated mechanism around the sample stage. In FIG. 3, only a portion substantially different from that in FIG. 1 is drawn, and an electrode 9, a position-resolved detector 10, and a slit 1 which constitute an energy analyzer.
The optical element 2 and the optical element 3 are both held by the support base 18. The support 18 can be moved by a moving mechanism 20 controlled by the controller 19.
According to the third embodiment, the movable devices are the optical element 3 and the energy analyzer, and the sample 4 may simply be held. Therefore, it becomes easy to install a mechanism for sample exchange.

In this embodiment, the optical element 3 for the light source 1 is used.
The position of changes. In this case, if an attempt is made to scan a condensing point on the surface of the sample 4, the condensing characteristics may change depending on the position of the optical element 3 and a difference in the plane resolution of analysis may occur, but the optical element 3 has a small aberration. By using a Wolter type mirror, the sample 4 can be two-dimensionally scanned without changing the plane resolution.

According to the third embodiment, the device structure around the energy analyzer can be made compact and the sample structure can be easily replaced.

(Embodiment 4) In Embodiment 4, the optical element 3 is installed inside the electrode 21 (FIG. 4). In this figure, only a portion substantially different from that in FIG. 1 is drawn, and since the energy analyzer used in the present invention uses a completely hemispherical electrode 21, electrons emitted from the sample 4 are All can be directed onto the position-resolved detector 10. In the above-described examples, a space for installing the optical element 3 is provided, so that a part of the electrode has to be removed. However, if it is possible to make the electrode 21 sufficiently large or the optical element 3 sufficiently small,
As in the fourth embodiment, the optical element 3 can be installed inside the electrode 21, and the maximum solid angle of electron uptake can be realized without cutting the electrode.

In the fourth embodiment, the optical element 3, the sample 4, the position-resolved detector 10, the slit 12, and the hemispherical electrode 2 are used.
1 is integrated and installed on the support base 22. In order to analyze while scanning the sample surface, the support table 22 is moved by the moving mechanism 24 controlled by the controller 23. Therefore, in the fourth embodiment as well, the positional relationship between the light source 1 and the optical element 3 changes during scanning, but as described in the third embodiment, if the scanning area is limited, the plane resolution does not change. Two-dimensional scanning of the sample 4 is possible.
Alternatively, if possible due to the device configuration, a moving mechanism may be added so that only the sample 4 can be moved independently.

According to the fourth embodiment, the solid angle for taking in the photoelectrons emitted from the sample can be maximized, and a larger signal intensity can be obtained.

(Fifth Embodiment) In the above-described embodiments, the position-resolving detector 10 is used in vacuum to
The angular distribution of photoelectron signal intensity was acquired. in this case,
The detector itself is expensive and complicated. In the fifth embodiment, a fluorescent plate 25 is installed, and the pattern reflected on the fluorescent plate is observed from outside the vacuum with a camera 26 or the like (FIG. 5). Further, an acceleration / deceleration electrode 27 controlled by the controller 11 is installed so that photoelectrons are incident on the fluorescent plate 25 with appropriate kinetic energy. The image obtained by the camera 26 is converted into data, which is taken into the computer 13 and subjected to necessary analysis.

According to the fifth embodiment, the position-resolved detector installed in a vacuum can be made simple, and the device can be made inexpensive and easy to maintain.

Although some embodiments have been described above, a method combining the methods of these embodiments is also sufficiently conceivable.

[0033]

As described above, in the sample surface analysis method and analyzer according to the present invention, light in the wavelength range from soft X-rays to vacuum ultraviolet is focused on a minute area of the sample surface. From the kinetic energy and angular distribution of photoelectrons emitted from it, it is possible to easily perform physical and chemical measurements such as depth direction analysis, band structure and crystal structure analysis in the microscopic region of the sample surface. Became.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an analyzer according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an analyzer according to a second embodiment.

FIG. 3 is a configuration diagram of an analyzer according to a third embodiment.

FIG. 4 is a configuration diagram of an analyzer according to a fourth embodiment.

FIG. 5 is a configuration diagram of an analyzer according to a fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Spectroscope 3 ... Optical element 4 ... Sample 5 ... Controller 6 ... Moving mechanism 7 ... Sample stand 8 ... Controller 9 ... Electrode 10 ... Position-resolved detector 11 ... Controller 12 ... Slit 13 ... Computer 14 ... Display Device 15 ... Support stand 16 ... Controller 17 ... Moving mechanism 18 ... Support stand 19 ... Controller 20 ... Moving mechanism 21 ... Electrode 22 ... Support stand 23 ... Controller 24 ... Moving mechanism 25 ... Fluorescent screen 26 ... Camera 27 ... Acceleration / deceleration electrode

Claims (27)

[Claims] 1. Identification of the sample surface from the kinetic energy distribution and emission angle distribution of photoelectrons emitted from the sample surface by irradiating the sample surface with light in the wavelength region from soft X-rays to vacuum ultraviolet rays. In a sample surface analysis method for analyzing the physical quantity or chemical quantity of a sample by mathematical means, the light is focused by an optical element to irradiate a minute area on the sample surface, and the movement of photoelectrons emitted from the sample surface A sample surface analysis method characterized by using an energy analyzer capable of simultaneously displaying the above-mentioned photoelectron emission angle distribution as a two-dimensional image for energy analysis. 2. The sample surface analysis according to claim 1, wherein the depth direction distribution of a specific element or its chemical state in the sample is measured by performing integral conversion on the emission angle distribution of the photoelectrons. Law. 3. The sample surface analysis method according to claim 1, wherein the band structure of the sample is measured by correlating the kinetic energy of the photoelectrons and the emission angle. 4. The sample surface analysis method according to claim 1, wherein the crystal structure of the sample is measured by performing integral conversion on the emission angle distribution of the photoelectrons. 5. The sample surface analysis method according to claim 1, wherein the electrode structure of the energy analyzer comprises a part of two concentric spheres. 6. The sample surface analysis method according to claim 1, wherein the electrode structure of the energy analyzer comprises a part of an ellipsoidal sphere. 7. A distribution of a physical quantity or a chemical quantity of the sample is measured in a specific area range on the sample surface by scanning a focal point of the light by the optical element on the sample surface. The sample surface analysis method according to claim 1, wherein 8. A three-dimensional distribution of a specific element or its chemical state is measured for a specific area range on the sample surface by scanning the light condensing point on the sample surface. The sample surface analysis method according to claim 2, wherein 9. The band structure distribution of the sample is measured with respect to a specific area range on the sample surface by scanning the focal point of the light on the sample surface. The sample surface analysis method according to claim 3. 10. The distribution of the crystal structure is measured in a specific region range on the sample surface by scanning the focal point of the light on the sample surface. The sample surface analysis method described in 1. 11. The method for scanning the light focusing point on the sample surface is to move the entire sample with respect to the fixed light focusing point. The sample surface analysis method according to any one of 1 to 10. 12. The method according to claim 7, wherein the method of scanning the light converging point on the sample surface is performed by moving the optical element. Sample surface analysis method. 13. The sample surface analysis method according to claim 1, wherein the optical element is a reflective optical element. 14. The sample surface analysis method according to claim 1, wherein the optical element is a diffractive optical element. 15. The sample surface analysis method according to any one of claims 1 to 12, wherein the optical element is a refractive optical element. 16. The sample surface analysis method according to claim 1, wherein the optical element is made of an appropriate combination of reflective, diffractive, or refractive optical elements. . 17. Means for condensing light in the wavelength region from soft X-rays to vacuum ultraviolet rays on the sample surface by an optical element,
Means for measuring the kinetic energy distribution of photoelectrons emitted from the sample surface, means for displaying the emission angle distribution of the photoelectrons as a two-dimensional image, and mathematical conversion of the detection signal obtained by each of the above means. And a means for analyzing a physical quantity or a chemical quantity related to the surface of the sample. 18. The sample surface analyzer according to claim 17, further comprising means for integrating and converting the detection signal, and measuring the depthwise distribution of the element of the sample or its chemical state. 19. The sample surface according to claim 17, further comprising means for associating a kinetic energy distribution of photoelectrons emitted from the sample surface with an emission angle distribution, and measuring a band structure of the sample. Analysis equipment. 20. The sample surface analyzer according to claim 17, further comprising means for integrating and converting the detection signal to measure a crystal structure of the sample. 21. A means for scanning the focal point of the light on the surface of the sample, according to any one of claims 17 to 20.
The sample surface analyzer according to any one of the above items. 22. The device according to claim 21, further comprising means for moving the entire sample with respect to the converging point in order to scan the converging point of the light on the surface of the sample. Sample surface analyzer. 23. The sample surface analyzer according to claim 21, further comprising means for moving the optical element in order to scan the light collecting point on the sample surface. 24. The sample surface analysis according to any one of claims 17 to 23, wherein the means for collecting the light on the sample surface is constituted by a reflection type optical element. apparatus. 25. The sample surface analysis according to any one of claims 17 to 23, wherein the means for collecting the light on the sample surface is composed of a diffractive optical element. apparatus. 26. The sample surface analysis according to any one of claims 17 to 23, wherein the means for collecting the light on the sample surface is constituted by a refraction type optical element. apparatus. 27. The means for condensing the light on the sample surface is constituted by an appropriate combination of reflective, diffractive or refractive optical elements.
The sample surface analyzer according to any one of items 7 to 23.