JP2007256038A - Surface analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface analyzer capable of suppressing position fluctuation of an irradiation electron beam, and performing image observation with high resolution and high magnification and analysis with high position accuracy. <P>SOLUTION: An electric field caused by electrification on a condenser element is shielded by placing a metal grid having a grounding potential between a sample and the condenser element, and position fluctuation of the irradiation electron beam is suppressed. By stopping deposition of a metal thin film on the condenser element, absorption of a soft X-ray by the metal thin film is prevented, to thereby improve detection sensitivity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention irradiates a sample with a primary beam such as an electron beam, an ion beam, or an X-ray, identifies an element existing in the vicinity of the surface of the sample by an electron beam, X-ray, light, etc. generated from the sample, and binds the sample. The present invention relates to a surface analysis apparatus using X-ray and / or light spectroscopy such as cathodoluminescence in a scanning electron microscope.

There is an X-ray analyzer as an apparatus for analyzing the composition, chemical state, etc. of the sample surface.
In such an X-ray analyzer, the sample surface is irradiated with finely focused electrons, and X-rays generated from the sample surface layer are focused by a condensing element, and wavelength dispersion using a semiconductor X-ray analyzer or a diffraction grating is performed. Type X-ray spectrometer, energy spectroscopy is performed here, the detected X-rays are detected by a detector, an energy spectrum is obtained, and the peak value, intensity, and shape of the spectrum are analyzed to analyze a micro area of the sample (Nano-order level) composition and chemical state are analyzed.

  As an example of a conventional ultra-high vacuum surface analyzer for detecting soft X-rays from a sample surface, the configuration will be described with reference to FIGS. An electron gun 4 is installed on the upper surface of the analysis chamber 1 to generate an electron beam 14 that irradiates the sample 2. An objective lens 5 is installed at the end of the electron gun 4 to focus the electron beam 14 on the sample 2 on the sample stage 3. On the side of the analysis chamber 1, there are a sample exchange chamber 12 for introducing the sample 2 into the analysis chamber 1 and a sample transport rod 13 for transporting the sample 2 to be measured introduced into the sample exchange chamber 12 to the analysis chamber 1. is set up.

When the sample 2 is irradiated with the electron beam 14, soft X-rays 15 are emitted from the sample surface 2. The analysis chamber 1 is kept at a very high vacuum of 10 ⁻⁸ Pa or less by a vacuum pump (not shown) or the like in order to keep the sample surface extremely clean and free from contamination particles when measuring low energy soft X-rays. Has been.

An X-ray spectrometer chamber 6 is installed on the oblique upper surface of the analysis chamber 1, and is maintained at a high vacuum of 10 ^{−7 to} 10 ⁻⁶ Pa by a vacuum pump (not shown). An X-ray condensing element 7, an aperture 8, and an X-ray spectrometer 10 are disposed on the axis of the condensing port of the X-ray spectrometer chamber 6.

  The X-ray condensing element 7 composed of a polycapillary or the like focuses the X-ray 15 generated on the sample 2 in the vicinity of the aperture 8. The aperture 8 has a circular minute mouth or slit shape for sizing the X-ray bundle 15 collected by the X-ray focusing element 7 in accordance with the incident conditions of the X-ray spectrometer 10. Further, the aperture 8 functions as a differential exhaust aperture for adjusting the beam shape of the X-ray bundle and maintaining a vacuum pressure difference between the analysis chamber 1 and the X-ray spectrometer chamber 6. The X-ray spectrometer 10 is installed in the X-ray spectrometer chamber 6. The X-ray spectrometer 10 performs energy spectroscopy on the X-ray bundle 15 beam-formed by the aperture 8 and projects (images) it on the X-ray detector 11. Diffraction grating, etc.).

  The operation will be described below. As shown in FIG. 2, the X-ray 15 generated by irradiating the sample 2 with the electron beam 14 is focused on the position of the aperture 8 by the X-ray condensing element 7. At this time, since the opening of the aperture 8 is sized according to the input conditions such as the angle and size of the X-ray spectrometer 10, unnecessary portions of the X-ray 15 are blocked and the X-ray beam shape is adjusted. The X-ray 15 beam-formed by the aperture 8 is subjected to energy spectroscopy by the X-ray spectrometer 10 and projected (imaged) on the X-ray detector 11. The imaged X-ray is converted into an electrical signal by the X-ray detector 11 and taken into a computer, where various arithmetic processes are performed and analysis is performed.

  In this way, in a device that irradiates a sample with a charged particle beam and separates X-rays or light generated therefrom, a condensing element (polycapillary lens, lens, concave mirror, etc.) is installed in front of the spectrometer. The X-ray and light generated from the sample are taken in as much as possible into the spectrometer to improve the detection sensitivity.

  However, these light condensing elements are made of an insulating material such as glass, and are installed as close to the sample as possible in order to increase the light condensing rate. This means that secondary electrons and reflected electrons generated from the sample are easily captured on the surface of the light collecting element and are charged with time, and charging on the light collecting element generates a new electric field. This new electric field forms a deflection field that is an unstable disturbance with respect to the electron beam 14. As a result, the irradiation point of the electron beam 14 fluctuates, and image observation with high resolution and high magnification is achieved. Analysis with positional accuracy becomes extremely difficult.

  In order to prevent adverse effects due to charging of these secondary electrons and reflected electrons, a metal thin film such as aluminum is vapor-deposited on the surface of the light condensing element to obtain a ground potential so as not to adversely affect the irradiated electron beam.

JP 2004-294168 A Japanese Patent Application No. 2004-362886

  Depositing a metal thin film on the light condensing element and setting it to ground potential has a great effect of preventing electrification, but conversely, this metal thin film absorbs soft X-rays, resulting in a large attenuation of the signal intensity. As a result, the detection sensitivity is greatly deteriorated.

  According to a first aspect of the present invention, there is provided an analysis chamber for holding a sample in a vacuum, primary beam irradiation means for irradiating the sample with a primary beam, and X-rays and / or light emitted from the sample. A surface analysis apparatus comprising: a condensing means for condensing; and a means for spectroscopic / detecting the condensed X-ray and / or light, wherein a metal grid having a ground potential between the sample and the condensing means Is a surface analysis device characterized in that

  The invention according to claim 2 is the surface analysis apparatus according to claim 1, wherein the primary beam is a charged particle beam.

  The invention according to claim 3 is the surface analysis apparatus according to claim 1 or 2, wherein the metal grid has a mesh shape and an aperture ratio is 90% or more.

  According to the present invention, the ground potential metal grid shields the electric field caused by the secondary electrons and reflected electrons captured by the light collecting element, so that the fluctuation of the position of the irradiated electron beam is suppressed, and the high resolution and high magnification can be achieved. Image observation and analysis with high positional accuracy are possible.

  As a result, it is not necessary to deposit a metal thin film on the condensing element, so soft X-ray absorption by the metal thin film is eliminated, and detection sensitivity is improved.

Example 1
Hereinafter, the configuration of the embodiment of the present invention will be described with reference to FIG. Since the description of each symbol is the same as in FIGS. 1 and 2, the description is omitted. FIG. 3 shows the case of detecting soft X-rays with particularly low energy. The difference from FIG. 2 is the presence or absence of the metal grid 16 at the ground potential between the light-collecting element 7 and the sample 2.

  FIG. 4 shows details of a mesh type grid as an example of the metal grid 16. The pitch is 1 mm, the bridge width is 0.05 mm, and the aperture ratio is 90% or more. By increasing the aperture ratio, the attenuation of the soft X-ray intensity by the grid is suppressed as much as possible.

  The operation of the present invention will be described below. In FIG. 3, irradiation with the electron beam 14 generates secondary electrons, reflected electrons, X-rays, light, etc. from the sample 2. Of these, secondary electrons, reflected electrons, etc. are detected by respective detectors not shown. Most are captured. However, some of the secondary electrons and reflected electrons pass through the space of the metal grid 16 in front of the light collecting element 7 and are charged on the light collecting element 7 to newly form an electric field.

  This electric field does not adversely affect X-rays and light, but as described above, forms a deflection field that is an unstable disturbance to the electron beam 14. However, since the metal grid 16 is at the ground potential, this unstable deflection field is confined between the condensing element 7 and the metal grid 16 and does not reach the path of the electron beam 14.

  As a result, even if there is a charge on the light condensing element, the irradiation point on the sample does not fluctuate, and high resolution, high magnification image observation, and analysis with high positional accuracy are realized. In addition, a metal thin film intended to prevent electrification of the condensing element, which has been conventionally required, is no longer necessary, and soft X-rays are not absorbed by the metal thin film, and detection sensitivity can be improved.

  In the present embodiment, an example of the case of X-ray detection by electron beam irradiation has been shown, but the same effect can be obtained when a cathode luminescence detector is attached to a scanning electron microscope to detect cathode luminescence by electron beam irradiation. I can do it.

  By installing a metal grid with a similar ground potential between the sample and the lens or concave mirror that is the condensing element of the cathode luminescence light, the electric field due to charging of secondary electrons and reflected electrons on the condensing element is shielded, Position fluctuation at the electron beam irradiation point is suppressed, image observation with high resolution and high magnification, and analysis with high position accuracy are realized. As a result, it is not necessary to deposit a metal thin film on the light condensing element, and the cathode luminescence light is not absorbed by the light condensing element, so that the detection sensitivity is improved.

It is a schematic diagram of the conventional ultrahigh vacuum X-ray spectrometer. It is a layout view of a sample, a condensing element, and an X-ray spectrometer of a conventional apparatus. It is the layout which attached the metal grid by this invention between the condensing element and the sample. It is a grid structure in the present invention.

Explanation of symbols

(Those that perform the same or similar operations are denoted by a common reference.)
DESCRIPTION OF SYMBOLS 1 Analysis chamber 2 Sample 3 Sample stage 4 Electron gun 5 Objective lens 6 X-ray spectrometer chamber 7 X-ray condensing element 8 Aperture 9 Partition valve 10 X-ray spectrometer 11 X-ray detector 12 Sample exchange chamber 13 Sample conveyance rod 14 Electron beam 15 X-ray 16 Metal grid

Claims (3)

An analysis chamber held in a vacuum containing the sample;
Primary beam irradiation means for irradiating the sample;
Condensing means for condensing X-rays and / or light emitted from the sample;
And a means for spectroscopically detecting and detecting the collected X-ray and / or light, wherein a grounded metal grid is disposed between the sample and the light collecting means. Surface analyzer.   The surface analysis apparatus according to claim 1, wherein the primary beam is a charged particle beam.   The surface analysis apparatus according to claim 1, wherein the metal grid has a mesh shape and an aperture ratio of 90% or more.

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