JPH0712763A - Surface analysis method and surface analysis device - Google Patents

Abstract

PURPOSE:To concurrently measure a reflected high-speed electron beam diffraction image with luminescence light by applying the constitution where the incident angle of an electron beam incident on sample surface becomes equal to or not more than the prescribed value. CONSTITUTION:A sample 4 is fixed to a sample holder 2 having a rotary and flap mechanism in a vacuum vessel 1. An electron beam 8 emitted from an electron gun 6 is incident on the surface of the sample 4 at an angle nearly in parallel thereto (10 degrees or less). The electron beam 8 is diffracted on the surface and a diffracted electron beam 8' reaches a phosphor screen 20. This screen 20 is thereby made luminous. As a result, reflected high-speed electron beam diffraction measurement can be undertaken about polar surface. Also, luminescence light 10 is emitted from the sample 4. This light 10 is converged through a lens system 12a and reflected with a total reflection mirror 12b. The light 10, then, passes a quartz glass window 14 and is taken out of the vessel 1. A spectrograph 16 and photo detector 18 are arranged outside the vessel 1 to spectroscopically measure the introduced light 10. In this case, a light shielding plate 13 is fitted, so as to prevent the light of the screen 20 from being incident on the lens system 12a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to surface analysis of semiconductors and ceramic materials, and more particularly to a surface analysis method and surface analysis apparatus using an electron beam.

[0002]

2. Description of the Related Art Development of semiconductor and ceramic thin films for application to electronic devices and optoelectronic devices has progressed, and techniques for controlling the size of thin films in nm size have been developed. For this reason, the surface analysis technique has become more and more important as a material analysis and evaluation method.
There are various surface analysis items such as composition, crystal structure, impurities, defects, and bonding state, which must be systematically interpreted using various measuring means.

One of the surface analysis methods is a method called cathodoluminescence method. This method measures the luminescence light generated by irradiating the sample surface with an electron beam,
The analysis is used to analyze the crystal perfection, impurities, crystal defects, strain field, etc. of the sample, and it is used as a method indispensable for the development of light emitting devices. In this cathodoluminescence method, as shown in FIG. 7, an electron beam 8 emitted from an electron gun 6 and accelerated to about 5 to 20 kV is vertically incident on the surface of a sample 4 placed inside a vacuum container 1. Then, the electron beam 8 causes the sample 4
Luminescence light 10 is generated on the surface of the. The luminescence light 10 is condensed by a condenser mirror 12, taken out of the vacuum container 1, separated by a spectroscope 16, and then converted into an electric signal by a photodetector 18.

The crystallinity and flatness of the sample surface are very important for the production of epitaxial thin films and superlattice thin films. The reflection high-energy electron diffraction (hereinafter abbreviated as RHEED) method is one of the evaluations of the crystal structure of the pole surface, and is widely used as an in-situ evaluation method particularly in the molecular beam epitaxial method. In the RHEED method, as shown in FIG. 8, 5 to 5 emitted from the electron gun 6 is applied to the surface of the sample 4 installed inside the vacuum container 1.
The electron beam 8 accelerated to about 30 kV is made incident substantially horizontally. Then, this electron beam causes diffraction on the surface of the sample 4. The diffracted electron beam 8'illuminates the fluorescent screen 20. A RHEED figure can be obtained by photographing this with the camera 21.

Further, recently, X generated during the RHEED measurement
RHEED-TRAXS (Reflection high-energy ele)
ctron diffraction-total reflection angle X-ray spe
ctroscopy) method was proposed (Shunji Hasegawa et. al.,
Jpn. J. Appl. Phys. 24, L387 (1985).). Figure 9 RHEE
The D-TRAXS device is shown. The X-rays 28 generated by electron beam irradiation are not uniformly emitted in all directions but are strongly emitted under the condition of total reflection. Therefore, the X-ray detector 30 is attached at the position of total reflection, and the position can be finely adjusted. The incident electron beam 8 is incident on the surface of the sample 4 at an angle substantially parallel to it, and the X-ray 28 from the substance on the surface is measured at an extraction angle close to the total reflection angle, so that the composition of the polar surface can be analyzed.

[0006]

However, in the above-mentioned cathode luminescence method, the high-speed electron beam is arranged so as to enter the surface of the sample substantially perpendicularly. Therefore, electrons penetrate deeply from the surface of the sample, and the depth thereof reaches about 1 to several μm depending on the acceleration voltage of the electron beam 8. Therefore, nm
It has the drawback that it cannot be applied to very-order polar surface analysis. In addition, the conventional RHEED can obtain information on the extreme surface of the crystal and atomic arrangement on the order of several atomic layers, but cannot obtain information on impurities and crystal defects. Furthermore, although the RHEED-TRAXS method can obtain information on the extreme surface of the crystal, atomic arrangement on the order of several atomic layers, flatness, and composition, it cannot obtain information on impurities and crystal defects. Therefore, an object of the present invention is to solve the problems of the cathodoluminescence method, the RHEED method and the RHEED-TRAXS method,
It is an object of the present invention to provide a surface analysis method and a surface analysis apparatus capable of analyzing crystallinity, flatness, impurities, and crystal defects of an nm-order pole surface at the same place at the same time.

[0007]

In order to solve the problems of the above-mentioned cathode luminescence method, the present invention is arranged for the cathode luminescence measurement so that the incident angle of the electron beam incident on the sample surface is 10 ° or less. It is characterized in that it is configured as follows. As the angle of incidence of the electron beam is made smaller, the depth of penetration of electrons into the sample surface becomes shallower, and especially at a shallow angle such that the surface of the sample is grazing, the penetration depth can be extremely shallow, a few nm. Therefore, the region where the luminescence light is generated can also be an extremely surface region having a depth of about several nm or less from the surface. Here, the penetration depth of the electron becomes deeper as the acceleration of the electron beam increases, but with the commonly used accelerating voltage of about 5 to 30 kV, it is possible to perform the polar surface analysis by setting the incident angle to several degrees or less. is there.

In order to solve the problems of the RHEED method, the present invention is characterized in that the luminescence light generated during the RHEED measurement is simultaneously measured. Since RHEED uses an electron beam, luminescence light is generated during measurement.
Also, since the electron beam is made to enter the sample surface smoothly,
Almost no penetration into the sample. Therefore, unlike the conventional method, the luminescence light contains only the signal from the polar surface. In the method of the present invention, a reflection high-speed electron beam diffraction measurement system including an electron gun and a fluorescent screen in a vacuum container, and a luminescence light generated from a sample surface by an electron beam emitted from the electron gun are collected and guided. An optical system for irradiating, the luminescence light is taken out of the vacuum chamber by the optical system, and a spectroscope and a photodetector for measuring the luminescence light are provided outside the vacuum chamber, and a RHEED image And luminescence light are measured at the same time.

Further, the surface of the material is scanned with an electron beam, the luminescence light generated by the electron beam is measured at each scanning point, and the RHEED image is measured at each scanning point. By analyzing these two-dimensionally, a two-dimensional surface analysis becomes possible. By narrowing the electron beam on the surface of the sample, it is possible to improve the resolution in the in-plane direction, particularly in the direction perpendicular to the electron beam.

In order to solve the problems of the RHEED-TRAXS method, the present invention is also characterized in that luminescence light generated during RHEED-TRAXS measurement is also measured.
Since the electron beam is smoothly incident on the sample surface, it hardly penetrates into the sample. Therefore, unlike the conventional method, the luminescence light contains only the signal from the polar surface. In this way, the RHEED image, X-rays and luminescence light are simultaneously measured.

[0011]

As described above, according to the present invention, by reducing the incident angle of the electron beam incident on the sample surface,
It is possible to evaluate crystal perfection, impurities, crystal defects, strain field, etc. on the ultra-surface on the order of nm or less. In addition, by simultaneously performing RHEED measurement and cathodoluminescence measurement,
It is possible to evaluate not only the crystal structure of the extreme surface but also crystal perfection, impurities, crystal defects, strain fields, and the like. Further, by scanning with an electron beam, a two-dimensional evaluation becomes possible. Also, in the conventional method, electrons that are incident almost perpendicularly to the sample surface lose their kinetic energy due to collision with the sample and remain on the sample surface, making it difficult to measure accurately because abnormal charging occurs with insulating materials. However, according to the method of the present invention, most of the electron beam is reflected on the sample surface, so that the charging can be significantly reduced.

[0012]

Embodiments of the present invention will be described with reference to the drawings. Unless otherwise required, the member numbers used in the prior art will be used. (Embodiment 1) FIG. 1 schematically shows a surface analysis apparatus of a first embodiment according to the present invention. A sample 4 is fixed to a sample holder 2 having a rotation and tilt mechanism inside the vacuum container 1. An electron gun 6 for exciting the sample 4 with electrons is attached. The sample 4 and the electron gun 6 are arranged so that the electron beam 8 emitted from the electron gun 6 is incident on the surface of the sample 4 at a shallow angle that is almost parallel. The electron beam 8 causes the sample 4 to glow. A parabolic focusing mirror 12 for focusing and guiding the luminescence light 10 generated from the sample 4 is mounted on the sample surface in the vacuum container 1. Instead of the parabolic focusing mirror 12, a lens or a reflecting mirror may be combined. The condensed luminescence light 10 passes through the quartz glass window 14 of the vacuum container 1 and is taken out of the vacuum container 1. A spectroscope 1 is provided outside the vacuum container 1.
6 and a photodetector 18 are installed to spectroscopically measure the guided luminescence light 10.

In this embodiment, as the sample 4, a mirror-finished sapphire and a gold thin film vapor-deposited thereon were used, and the luminescence light 10 was spectroscopically measured with the incident angle of the electron beam 8 being about 2 °. The results are shown in FIG. 2 and FIG.
Shown in. FIG. 3 shows luminescence spectra from sapphire and a sample obtained by vapor-depositing a gold thin film on sapphire to a thickness of 5 nm and 12 nm, respectively. A strong peak near 326 nm, a very sharp peak at 692 nm and 694 nm, and a broad peak near 737 nm were observed, and the intensities of these peaks became sharply weaker when the gold deposition film was thickened. Also, FIG.
The dependence of the peak intensities at 326 nm, 694 nm, and 737 nm on the gold film thickness is shown, and it can be seen that the film thickness dependence depends on the peak. As described above, according to the present invention, it becomes possible to measure luminescence on the order of depth nm.

(Embodiment 2) FIG. 4 shows a block diagram of a surface analysis apparatus according to a second embodiment of the present invention. Inside the vacuum container 1, there is a sample holder 2 with a rotating and tilting mechanism, and a sample 4 is fixed to this sample holder 2. Electron gun 6
And the fluorescent screen 20 are provided on both sides of the sample 4 respectively.
The electron beam 8 emitted from the electron gun 6 is incident on the surface of the sample 4 at a shallow angle which is almost parallel to each other. The electron beam 8 incident on the surface of the sample 4 is diffracted on the surface, and the diffracted electron beam 8 '
Reaches the fluorescent screen 20 and makes it glow. This allows RHEED measurements.

A lens system 12 for collecting the luminescence light 10 generated from the sample 4 in the vacuum container 1.
A and a light guide system 12b (in this case, a total reflection mirror) for taking out the condensed light to the outside of the vacuum container are attached. An optical fiber may be used for the light guide system 12b in addition to the reflection mirror. The light of the screen 20 is the lens 1
A light shielding plate 13 is attached so as not to enter the inside of 2a. A spectroscope 16 is attached to the outside of the vacuum container 1 to spectroscopically measure the luminescence light 10 from the sample 4. Since the electron beam 8 is incident on the sample surface substantially in parallel, it hardly penetrates into the sample 4. Therefore, the luminescence light 10 generated from the sample 4 is limited to that from the sample surface. In this way, the RHEED image of the pole surface and the cathodoluminescence measurement can be performed simultaneously and at the same location.

(Embodiment 3) FIG. 5 shows a block diagram of a surface analysis apparatus according to a third embodiment of the present invention. The basic configuration is the same as in the second embodiment. The difference is the electron beam 8 emitted from the electron gun 6.
The point is that the diameter of the sample surface can be narrowed from several nm to several μm, and the electron beam 8 can be two-dimensionally scanned on the sample surface. Then, while scanning, RHEED and cathodoluminescence are simultaneously measured at the same place, and the computer 2
Processing is performed at 4 to perform two-dimensional evaluation. Therefore, the electron gun 6
Controller 22, computer 24 for scanning
Is attached. Further, a photomultiplier 26 is attached to measure the intensity of the reflected and diffracted electrons. A scanning reflection electron microscope image can be obtained by using the intensity of the reflected diffraction electrons as a luminance signal.

(Embodiment 4) FIG. 5 shows a block diagram of a surface analyzer according to a fourth embodiment of the present invention. Inside the vacuum container 1, there is a sample holder 2 with a rotating and tilting mechanism, and a sample 4 is fixed to this sample holder 2. Electron gun 6
And the fluorescent screen 20 are provided on both sides of the sample 4 respectively.
The electron beam 8 emitted from the electron gun 6 is attached to the sample surface so as to face each other at a shallow angle which is almost parallel to the sample surface. The electron beam 8 incident on the sample surface is diffracted on the surface and reaches the fluorescent screen 20 to illuminate it. This allows RHEED measurements.

Further, the characteristic X from the sample 4 by the electron beam 8
Line 28 occurs. Since the electron beam 8 is gradually incident on the sample surface, the incident electrons excite many surface atoms, and the intensity of the characteristic X-ray 28 from the surface atoms becomes strong. The intensity of the characteristic X-rays 28 from the surface atoms is much higher than that of X-ray microanalysis in which a normal electron beam is vertically incident. Further, the characteristic X-rays 28 are not emitted uniformly in all directions, but are emitted strongly in a specific direction. This azimuth corresponds to the critical angle of the total reflection of the characteristic X-ray 28 with respect to the solid surface. The X-ray detector 30 (Si (Li) detection element) is attached in this direction. The X-ray 28 excited by the electron beam 8 is extracted to the outside of the vacuum container 1 through the Be window 32 for maintaining a vacuum, enters the X-ray detector 30, and is detected.

Further, inside the vacuum container 1, a lens system 12 for collecting the luminescence light 10 generated from the sample 4 and taking it out of the vacuum container 1 is attached.
Luminescence light 1 from the sample 4 by the lens system 12
0 is guided to the spectroscope 16 and spectroscopically measured. Since the electron beam 8 is incident on the sample surface substantially in parallel, it hardly penetrates into the sample 4. Therefore, the luminescence light 10 generated from the sample 4 is limited to that from the sample surface.
In this way, the RHEED image of the pole surface, the X-ray spectroscopic measurement and the cathodoluminescence measurement can be performed at the same measurement site and simultaneously. Further, an electron beam is two-dimensionally scanned on the sample surface, and three kinds of measurements are performed at each scanning point, so that accurate and precise evaluation can be performed on the sample surface.

[0020]

As described in detail above, according to the present invention,
Since the luminescence light on the pole surface can be measured, impurities and crystal defects on the pole surface can be analyzed. Moreover, since RHEED and cathodoluminescence evaluation can be performed simultaneously and at the same measurement site, the surface crystal structure, impurities, and crystal defects can be evaluated. Furthermore, since RHEED, cathodoluminescence and X-ray spectroscopic measurement can be performed at the same measurement site, surface composition can be evaluated in addition to surface crystal structure, impurities and crystal defects, and systematic and reliable High surface analysis can be performed. Further, according to the present invention, a plurality of analysis techniques can be combined to easily perform advanced surface analysis.

[Brief description of drawings]

FIG. 1 is a block diagram of a surface analysis device by a cathodoluminescence method.

FIG. 2 is a diagram showing the relationship between sapphire and sapphire vapor-deposited with gold and the intensity of cathode luminescence.

FIG. 3 is a spectrum showing the dependence of the emission intensity of sapphire on the thickness of a gold thin film.

FIG. 4 is a configuration diagram of a surface analysis device by a RHEED method and a cathodoluminescence method.

FIG. 5 is a block diagram of a surface analysis apparatus by a RHEED method and a cathodoluminescence method capable of scanning the sample surface with an electron beam.

Figure 6: RHEED method, cathodoluminescence method and TRAX
Configuration diagram of the surface analyzer by S method

FIG. 7 is a configuration diagram of a conventional cathode luminescence device.

[Figure 8] Configuration diagram of a conventional RHEED device

[Figure 9] Configuration diagram of a conventional RHEED-TRAXS device

[Explanation of symbols]

 1 vacuum container 4 sample 6 electron gun 8 electron beam 10 luminescence light 28 X-ray

Claims (4)

[Claims] 1. A cathode luminescence method in which a sample surface is irradiated with an electron beam in vacuum to measure luminescence light generated from the sample surface, wherein an incident angle of the electron beam incident on the sample surface is 10 ° or less. A method for surface analysis, characterized in that 2. A reflection high-energy electron diffraction measurement system composed of an electron gun and a fluorescent screen in a vacuum, and a cathode luminescence measurement system for measuring luminescence light generated from a sample surface by an electron beam emitted from the electron gun. A surface analysis device characterized by being provided. 3. A reflection high-energy electron diffraction measurement system composed of an electron gun and a fluorescent screen in a vacuum, and a cathode luminescence measurement system for measuring luminescence light generated from a sample surface by an electron beam emitted from the electron gun. And a surface analysis device, wherein the electron beam is provided so as to scan the surface of the sample. 4. A reflection high-energy electron diffraction measurement system composed of an electron gun and a fluorescent screen in vacuum, and a measurement system for measuring X-rays generated from a sample surface by an electron beam emitted from the electron gun. And a cathode luminescence measuring system for measuring luminescence light generated from a sample surface by an electron beam emitted from the electron gun.