Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Reexamination Certificate
2000-03-10
2002-11-05
Lee, John R. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
C250S306000, C250S307000
Reexamination Certificate
active
06476389
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 11-080822 filed on Mar. 25, 1999, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an X-ray analyzer, mounted to a scanning electron microscope (SEM) or the like, for carrying out element analysis of a specimen according to characteristic X-rays emitted therefrom upon irradiation with electron beams; and an analyzing method using the same.
2. Description of the Prior Art
Among specimen observing apparatus such as scanning electron microscope (SEM) and the like, there have been known those which qualitatively or quantitatively analyze elements contained in a specimen by analyzing a spectrum of characteristic X-rays generated from the specimen upon irradiation with electron beams.
When elements contained in the specimen are to be analyzed quantitatively, it has been desired that, since the irradiation current value of electron beams with respect to the specimen fluctuates greatly, this value be monitored and the measured X-ray dose be calibrated based thereon in an energy dispersive X-ray analyzer, for example, so as to improve the accuracy in quantitative analysis.
However, it is not always easy to correctly measure the irradiation current value during the final analysis of the specimen. Therefore, in conventional techniques, it has been assumed, for example, that the irradiation current value of electron beams in SEM does not vary in a short period such as an analyzing time, and the irradiation current value is measured by use of a Faraday cage, or the irradiation current value is computed according to the measured X-ray dose of a specific reference sample, so as to determine the irradiation current value during the final analysis of the specimen.
However, the irradiation current value of electron beams in an SEM varies in a short period of time such as the final measuring time in practice, such that the assumed irradiation current value of electron beams differs from the actual one, thereby making it difficult to greatly improve the accuracy in quantitative analysis.
In view of such circumstances, it is an object of the present invention to provide an X-ray analyzer with a simple configuration which can determine an accurate irradiation current value of electron beams during measurement of a specimen when carrying out quantitative analysis of elements contained in the specimen by detecting characteristic X-rays generated from the specimen upon irradiation with the electron beams, thereby greatly improving the accuracy in analysis of elements contained in the specimen; and an analyzing method using the same.
In SEMs equipped with a field emission type (FEG type) electron gun, since the irradiation current of electron beams fluctuates more greatly than in other SEMs, it is necessary to monitor the irradiation current of electron beams during the final measurement of the specimen even if the configuration of the apparatus is somewhat complicated thereby.
Therefore, conventional FEG type SEMs use irradiation current measuring means or the like comprising a Faraday cage provided with an aperture for transmitting electron beams or the like, disposed on the electron beam source side from the specimen, so as to monitor a part of irradiation current of electron beams during the final measurement of the specimen, and calibrate the measured X-ray dose based thereon. In the FEG type SEMs, however, the cross-sectional intensity distribution of the irradiation current flux changes with time because of the fact that the surface state of the filament of the electron gun changes with time, and so forth, so that the irradiation current value detected by the irradiation current measuring means or the like is not proportional to the actual irradiation current value upon the specimen, whereby it has been difficult to greatly improve the accuracy in quantitative analysis.
In view of such circumstances, it is an object of the present invention to provide an X-ray analyzer which can determine a correct irradiation current value of electron beams during measurement of a specimen even when carrying out quantitative analysis of elements contained in the specimen by detecting characteristic X-rays generated from the specimen upon irradiation with the electron beams in an FEG type SEM, thereby greatly improving its accuracy in analysis; and an analyzing method using the same.
SUMMARY OF THE INVENTION
The present invention achieves the above-mentioned objects by monitoring an absorption current value which has a good proportional relationship with the irradiation current value of an electron beam irradiating the specimen, and determining the irradiation current value of the electron beam according to the result of monitoring.
Namely, a first X-ray analyzer in accordance with the present invention is an X-ray analyzer comprising an electron beam source for generating an electron beam, electron beam converging means for converging the electron beam onto a specimen, and an X-ray detecting section for detecting a characteristic X-ray generated from the specimen upon irradiation with the electron beam;
the X-ray analyzer comprising:
an absorption current measuring section for measuring an absorption current value from the specimen and measuring an absorption current value from a reference sample disposed so as to be interchangeable with the specimen;
a proportionality factor calculating section for calculating a value of ratio A between respective absorption current values in the specimen and reference sample; and
reference sample absorption current calculating means for calculating, when the specimen is finally measured, an absorption current value of the reference sample at each measuring time by multiplying each measured absorption current value of the specimen by the value of ratio A determined by the proportionality factor calculating section.
A second X-ray analyzer in accordance with the present invention is an X-ray analyzer comprising an electron beam source for generating an electron beam, electron beam converging means for converging the electron beam onto a specimen, and an X-ray detecting section for detecting a characteristic X-ray generated from the specimen upon irradiation with the electron beam;
the X-ray analyzer comprising:
an absorption current measuring section for measuring an absorption current value from the specimen;
an irradiation current measuring section disposed at a part of positions where the electron beam passes;
a proportionality factor calculating section for calculating a value of ratio C between the absorption current value in the specimen measured by the absorption current measuring section and an irradiation current value measured by the irradiation current measuring section substantially simultaneously with when the absorption current value is measured by the absorption current measuring section; and
means for calculating, when the specimen is finally measured, an irradiation current value to be measured by the irradiation current measuring section at each measuring time from an absorption current value in the specimen or a reference sample disposed interchangeable with the specimen by multiplying each measured absorption current value of the specimen by the value of ratio C determined by the proportionality factor calculating section.
A third X-ray analyzer in accordance with the present invention is an X-ray analyzer comprising an electron beam source for generating an electron beam, electron beam converging means for converging the electron beam onto a specimen, and an X-ray detecting section for detecting a characteristic X-ray generated from the specimen upon irradiation with the electron beam;
the X-ray analyzer comprising:
an absorption current measuring section for measuring an absorption current value from the specimen and measuring an absorption current value from a reference sample disposed so as to be interchangeable with the specimen;
an irradiation current measuring section disposed at
Konakawa Hiroshi
Sato Yasuhiko
Suzuki Seiichi
Fuji Photo Optical Co., Ltd.
Lee John R.
Snider Ronald R.
Snider & Associates
Vanore David A.
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