Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Reexamination Certificate
1999-12-15
2001-03-13
Anderson, Bruce C. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
C378S045000
Reexamination Certificate
active
06201241
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an analyzer of organic substances for analyzing a specimen containing organic substances by irradiation of electron beam to the specimen and by performing spectroscopy of fluorescent light emitted from the specimen.
As the conventional methods to analyze organic substances, various methods have been known such as nuclear magnetic resonance method (NMR), infrared spectroscopy, Raman spectroscopy, ultraviolet excitation fluorescence spectroscopy, electron spectroscopy for chemical analysis (ESCA) or X-ray photoelectron spectroscopy (XPS), etc.
As a method to identify and discriminate organic substances using the ultraviolet excitation fluorescence spectroscopy, a method described in “Analyzer for Organic Foreign Substances in Micro-Area Using Micro-Fluorescence Spectroscopy” (Hitachi Review issued in Japan, Vol.73, No.9, September 1991) is known.
However, when the above methods such as nuclear magnetic resonance method (NMR), infrared spectroscopy, Raman spectroscopy, ultraviolet excitation fluorescence spectroscopy, or ESCA (XPS) method are used, measurable range on the specimen is as follows: 100 &mgr;m or more in the nuclear magnetic resonance method (NMR), 7 &mgr;m or more in the infrared spectroscopy method, 1 &mgr;m or more in the ultraviolet excitation fluorescence spectroscopy method, 1 &mgr;m or more in the Raman spectroscopy, and 10 &mgr;m or more in the ESCA (XPS) method. In none of the above methods, it is possible to analyze organic substance in micro-area, i.e. in size of 1 &mgr;m or less.
In the method to discriminate and identify organic substances using ultraviolet excitation fluorescence spectroscopy, as seen in the above literature, fluorescence wavelength range of fluorescent light emitted from the specimen under bombardment of ultraviolet ray is narrow. For example, even when ultraviolet ray with wavelength of 360 nm is bombarded, wavelength of the emitted fluorescent light is limited to that of 450 nm or around. This means that there is limitation in the information obtained for identification of the organic substances.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an analyzer, by which it is possible to perform measurement even in the range of 1 &mgr;m or less, to obtain as much information as required for identification of organic substances, to improve accuracy in classification and identifying the organic substances, and to raise detection efficiency by efficiently converging fluorescent light.
To attain the above object, the analyzer for organic substances according to the present invention comprises a irradiation unit for irradiating a specimen containing organic substances with an electron beam, a spectrum detection unit for detecting spectrum of fluorescent light emitted from the specimen, a storage unit for storing shape of a reference spectrum of fluorescent light when the electron beam is irradiated to a specific organic substance, and a searching unit for classification and identifying organic substances in the specimen by comparing the shape of the reference spectrum stored with the detected spectrum. Also, in the analyzer for organic substances of the present invention, comparison of shapes of the spectra is performed at least by comparing number of spectral peaks, wavelength at position of each peak, half width value of each peak, and difference or ratio of peak values. Further, in the analyzer of organic substances of the present invention, comparison of shapes of spectrum is performed by taking the change of spectral shape due to damage caused by the electron beam bombardment into account. Further, in the analyzer for organic substances of the present invention, the storage unit also stores reference spectrum of characteristic X-ray generated when the electron beam is bombarded each specific type of substance. Also, in the analyzer of organic substances of the present invention, a reflective optical element is arranged on an optical axis between the specimen and the spectrum detecting unit and the reflective optical element comprises an entry transmitting surface, an exit transmitting surface in shape of a slit designed with the shape of the entry transmitting surface compressed at least in one direction, and a reflection surface which is provided around an optical axis between the entry transmitting surface and the exit transmitting surface and is used for reflecting fluorescent light and guiding it toward the exit transmitting surface. According to the present invention, the electron beam is irradiated and fluorescent light emitted under bombardment of the electron beam is analyzed to discriminate and identify the organic substances. Even in the range of 1 &mgr;m or less, measurement can be performed. It is possible to perform measurement in the range of micro-area, and the electron beam having higher energy than light is irradiated for analysis. Therefore, even in ultraviolet range, fluorescent light with spectrum in wide range is emitted from the specimen, and it is possible to obtain much information and to improve accuracy in classification and identifying organic substances.
REFERENCES:
patent: 5418826 (1995-05-01), Sato et al.
patent: 5425916 (1995-06-01), Beer et al.
patent: 5596195 (1997-01-01), Obori et al.
patent: 5635716 (1997-06-01), Liu et al.
patent: 5674743 (1997-10-01), Ulmer
patent: 5712165 (1998-01-01), Alvarez et al.
Anderson Bruce C.
Kabushiki Kaisha Topcon
Nields & Lemack
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