JPH04140652A - Electron spectroscopy analyzer - Google Patents

Abstract

PURPOSE:To reduce a size of an entire apparatus by generating plasma with laser light applied to a target and generating white soft X-rays from the plasma so that a so-called X-ray plasma light source is used. CONSTITUTION:A YAG laser light source 4 applies laser light onto a target 3 to generate X-rays, and a concave diffraction grid 6 disperses the X-rays. When the laser light from the light source 4 is slantly incident from a transparent window 2 by a condenser lens 5 and applied to a surface of the target 3, a part of the target 3 is solved to be vaporized and be plasma, from which white soft X-rays are generated. Then the grid 6 disperses the soft X-rays generated from the plasma, the dispersed rays pass through a slit 7 to be incident to a sample 10 while generated secondary electrons are subjected to electron spectroscopy 12, the electron energy is detected by a microchannel plate 13, and then obtained spectroscopic spectrum of the secondary electrons is analyzed. Thus by using a so-called plasma light source, an electron spectroscopy analyzer can be reduced in size.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electron spectrometer that examines the properties of a sample by spectroscopically measuring secondary electrons generated from a sample irradiated with X-rays. be.

[Problems to be solved by conventional techniques and inventions] In recent years,
Soft X with long wavelengths of several angstroms or more is used in fields such as surface analysis of semiconductor materials, analysis of organic materials containing carbon in particular, analysis of semiconductor processes such as CVD, evaluation of organic electronic devices, and analysis of other biological materials. ES CA (Electron 5pec
troscopy for ChemicalAnal
Evaluation using methods such as electron spectroscopy (nsis: electron spectrochemical analysis) and Auger electron spectroscopy is required.

However, since current commercially available evaluation devices use an X-ray tube as a light source, they can only use characteristic X-rays with short wavelengths of several angstroms or less. In the characteristic X-ray region with a short wavelength of several angstroms or less, the absorption coefficient of organic substances mainly composed of carbon is small, and the generation rate of secondary electrons and Auger electrons is poor, resulting in poor analysis sensitivity. In addition, since only X-rays of specific wavelengths can be used, multifaceted analysis is not possible. This is particularly disadvantageous when identifying elements. Currently, an SOR (synchrotron radiation) light source is required to utilize white soft X-rays.

However, since SOR light sources require large-scale facilities, they are out of reach for general users.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a compact electronic spectrometer that is accessible to general users.

[Means and effects for solving the problem] The electron spectrometer according to the present invention includes a light source that generates X-rays by irradiating a target placed in a vacuum container with a laser beam, and an X-ray emitted from the light source.
a concave diffraction grating provided in a vacuum container for spectroscopy; a slit movable along the Rowland circle of the concave diffraction grating in the optical path diffracted by the concave diffraction grating; and a test sample. a sample stage that can move along with the movement of the slit so that the X-rays passing through the slit hit the test sample; and an electron spectrometer and a detector that receive secondary electrons generated from the test sample. It is characterized by

According to the above configuration, a so-called X-ray plasma light source is used as a white soft X-ray light source, in which a target is irradiated with laser light to generate plasma, and soft X-rays are generated from the plasma. Since the X-ray plasma light source is small,
The entire device can be downsized.

This will be explained in detail below.

In a vacuum of 10-'Torr or less, when a target such as a metal is irradiated with a laser beam with an intensity of 1012 W/Cl11 or more, the metal of the target becomes a plasma state and white soft X-rays with a wavelength of 5 Å or more are generated. do. To achieve this, all that is needed is a commercially available YAG laser light source and a small vacuum container, and an extremely compact soft X-ray light source can be realized. In addition, in order to disperse light in the soft X-ray region over a wide range, an oblique input spectrometer is superior to a window-side rectangular spectrometer. By providing a slit on the Rowland circle of this spectrometer, a specific wavelength can be extracted. By irradiating the sample surface with monochromatic X-rays that have passed through this slit, and analyzing the energy of the generated secondary electrons using an electron spectrometer installed at a specific observation angle, elements on the sample surface can be identified. That is, by observing the energy of photoionized electrons and Auger electrons emitted from the sample surface, it can be determined which element and at which energy level electrons are emitted in large numbers. Furthermore, by selecting the wavelength of the X-rays to be irradiated, the amount of Auger electrons observed from a specific element can be increased. For example, if carbon is irradiated with X-rays with a wavelength near the absorption edge, the emission kinetic energy will be 400 eV.
It is possible to preferentially observe Auger electrons in KLL carbon.

This determines the carbon content on the sample surface. By changing the wavelength of the X-rays, we can observe Auger electrons from other elements. This shows that elemental analysis can be performed with higher sensitivity than conventional ESCA using an X-ray tube. Furthermore, if an X-ray condensing optical system is installed after the slit, an X-ray microbeam is formed, and a two-dimensional image of the element distribution to be observed can be taken by scanning the sample stage. An electron spectrometer is composed of two planar electrodes, one of which has an entrance and exit slit, or two spherical or cylindrical electrodes.

Note that the sample stage and the slit may be arranged in a vacuum container, and the entire vacuum container may be moved along with the movement of the slit.

〔Example〕

Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

FIG. 1 is a schematic diagram of a first embodiment of an electron spectrometer according to the present invention.

Reference numeral 1 denotes a large vacuum container having a transparent window 2, in which a cylindrical target 3 is provided so as to be rotatable around a central axis by a rotation mechanism (not shown). 4 is a YAG laser light source placed outside the vacuum container l;
Reference numeral 5 denotes a condensing lens for condensing laser light, which allows the laser beam from the laser light source 4 to enter obliquely through the transparent window 2 (the reflected light from the transparent window 2 returns to the laser light source 4). (To prevent the operation of the laser light source 4 from becoming unstable)
When the surface of the target 3 is irradiated, a part of the target 3 melts and evaporates into plasma, and from this plasma soft X
Lines are now appearing.

Reference numeral 6 denotes a concave diffraction grating that is provided within the vacuum vessel 1 and separates soft X-rays generated from the plasma. Reference numeral 7 denotes a slit which is fixed on a support base 8 so as to be located on the Rowland circle of the concave diffraction grating 6 in the vacuum container l, through which soft X-rays from the concave diffraction grating 6 pass; Soft X that is rotatably attached to the top and passed through slit 7
This is a sample holder in which a sample 10 is fixed at a position where the line strikes, and the support stand 8 is attached to the vacuum vessel 1 so that the slit 7 can move on the Rowland circle of the concave diffraction grating 6.
It is possible to move against. Reference numeral 11 denotes an electron spectrometer support stand attached to the support stand 8 so as to be able to rotate around the rotation center of the sample holder 9 in the vacuum container 1. A cylindrical mirror type electron spectrometer 12 and the spectrometer 1
A microchannel plate 13 for detecting the energy of the electrons spectrally separated by 2 is fixed. The output signal of the microchannel plate 13 is guided outside the vacuum container 1 and supplied to a signal processing system (not shown).

Since this embodiment is configured as described above, when the laser light source 4 is oscillated and the target 3 is irradiated with laser light,
A part of the target 3 melts and evaporates into plasma, and soft X-rays are generated from this plasma. Incidentally, if a part of the target 3 evaporates and becomes depressed, the target 3 is rotated so that the laser beam always hits a new surface. Soft X generated
The beam enters the concave diffraction grating 6 and is spectrally separated, and then passes through the slit 7 and enters the sample 10, and the secondary electrons generated in the sample 10 are spectrally separated by the electron spectrometer 12. The energy of the emitted electrons is detected by the microchannel plate 13, and the output signal of the microchannel plate 13 is processed by a signal processing system (not shown) to obtain a spectroscopic spectrum of the secondary electrons emitted from the sample 10.

Then, by analyzing this spectroscopic spectrum, the surface state of the sample IO is analyzed.

In the above analysis, by rotating the sample holder 9, the soft X-rays can be made incident on the sample 10 at various angles. Furthermore, by rotating the electron spectrometer support stand 11, secondary electrons generated from the sample IO can be measured from various directions. Furthermore, by driving the support base 8 and moving the slit 7 on a Rowland circle, the wavelength of the soft X-rays irradiated onto the sample 10 can be scanned and the amount of secondary electrons generated can be measured.
Extended X-ray Absorption
FineStructure) analysis is also possible. Furthermore, an electron multiplier tube may be used instead of the microchannel plate 13.

The operating principle of this embodiment has been explained above, but this embodiment uses a so-called soft X-ray plasma light source.
Since the line plasma light source is small, the entire device can be downsized. Also, recently, oxygen (K absorption edge 23.32
), nitrogen (K edge 30.99 people), carbon (K edge 43.68 people), phosphorus (L edge 94 people, K edge 5.8
human), calcium (L absorption edge 35 human), sodium (K
There is active research on biological materials such as magnesium (K absorption edge 9.5) and magnesium (K absorption edge 9.5), and analysis using soft X-rays with a long wavelength of 5 Å or more as a probe is required. The electron spectrometer according to the invention can be said to be optimal.

FIG. 2 is a schematic diagram of the second embodiment, which is characterized by the fact that an X-ray focusing optical system (Walter mirror optical system) 14 is arranged between the slit 7 and the sample 10, and the sample holder 9
The target 3. can move in two directions perpendicular to the direction of incidence of soft X-rays on the sample 1o, the electron spectrometer 12 has a coaxial cylindrical shape, and the target 3. Although the concave diffraction grating 6 and the members after the slit 7 are connected, they are provided in separate vacuum vessels 1, 5, 16 and 17 so that the entire vacuum vessel 17 moves as the slit 7 moves. This embodiment differs from the first embodiment in that

According to this embodiment, since the soft X-rays are concentrated in a narrow area on the sample 10 by the X-ray condensing optical system 14, it is possible to measure the properties of the substance at the focal point. If you scan the entire surface of
The distribution of substances on the sample 10 can be measured.

There are various types of electron spectrometers, and representative examples are shown below.

(1) Parallel plane electrostatic electron spectrometer (Figure 3) A certain voltage is applied between two electrode plates,
Among the charged particles incident through the slit, only charged particles with a specific kinetic energy are deflected and allowed to pass through the exit slit. By scanning the voltage applied to the two electrodes,
The energy of charged particles can be analyzed. Note that the entrance slit and the exit slit are located at the same distance from the lower electrode of the spectrometer. The condition for secondary focusing is R/a=6r.

(2) Coaxial cylindrical electrostatic electron spectrometer (Fig. 4) Again,
A certain voltage is applied between two cylindrical electrode plates, and the entrance and exit slits are placed between the two cylindrical electrode plates. Among the charged particles that enter through the entrance slit, those with a specific kinetic energy are deflected, travel on a circular trajectory between the electrodes, and can pass through the exit slit. Note that the entrance slit and the exit slit are curved to reduce the boundary electric field effect.

(3) Hemispherical electrostatic electron spectrometer (Fig. 5) The principle is the same as that of the coaxial cylindrical electrostatic electron spectrometer. but,
Since the deflection electrode plate is spherical, it is possible to analyze the energy of charged particles at various angles of incidence, making it a bright spectrometer.

(4) Cylindrical mirror electrostatic electron spectrometer (
(Fig. 6) The principle is almost the same as that of a plane-parallel electrostatic electron spectrometer. However, since the deflection electrode plate is cylindrical, it is possible to analyze the energy of charged particles at various angles of incidence, making it a bright spectrometer.

Note that the cut portion of the inner cylinder is partially closed for mechanical fixation. This hole is covered with wire mesh to make the electric field uniform. Boundary electric field correction electrodes are attached to the ends of the inner and outer cylinders as in the parallel plate analyzer, but are omitted from the diagram for simplicity.

(5) Field-blocking electrostatic electron spectrometer (Figure 7) Basically, the potential of the sample that emits charged particles is grounded, and a counter electrode is provided to provide a potential to the sample that emits charged particles. Apply a polar potential that causes attraction. On the other hand, the grid applies a polar potential to push the charged particles back from the electrode side.

Among the secondary electrons generated from the sample surface, those with more than a certain kinetic energy pass through the grid and reach the counter electrode. The signal is observed as a current flowing between the electrode and ground. By scanning the grid potential and taking the difference between the current values, it is possible to analyze the energy of secondary electrons.

In addition, when the kinetic energy of the charged particles to be analyzed is large, there are many electron spectrometers that deflect using a magnetic field instead of an electric field.

〔Effect of the invention〕

As described above, the electron spectrometer according to the present invention has the important practical advantage of being small enough to be accessible to general users.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a first embodiment of an electron spectrometer according to the present invention, FIG. 2 is a schematic diagram of a second embodiment, and FIGS.
The figures are diagrams showing various examples of electron spectrometers. 1.15, 16.17... Vacuum container, 2... Transparent window, 3... Target, 4... YAG laser light source, 5... Condensing lens, 6... ...Concave diffraction grating, 7...Slit, 8...Support, 9...
Sample holder 10...Sample, 11...
・Electron spectrometer support stand, 12...Electron spectrometer, 13.
...Microchannel plate, 14...X-ray focusing optical system.

Claims (2)

[Claims] (1) A light source that generates X-rays by irradiating a laser beam onto a target placed in a vacuum container; and a concave diffraction grating provided in the vacuum container to separate the X-rays from the light source; A slit movably provided along the Rowland circle of the concave diffraction grating in the optical path diffracted by the concave diffraction grating, and a test sample placed thereon so that the X-rays passing through the slit hit the test sample. An electron spectrometer comprising: a sample stage that can move with the movement of the slit; and an electron spectrometer and a detector that receive secondary electrons generated from the test sample. (2) Electron spectroscopy according to claim (1), wherein the sample stage and slit are arranged in a vacuum container, and the entire vacuum container moves with the movement of the slit. Analysis equipment.