Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Patent
1997-12-18
1999-08-10
Nguyen, Kiet T.
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
H01J 37244
Patent
active
059362448
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to electron microscopes and electron microscopic methods and more particularly, to an electron microscope and an electron microscopic method which are suitable for observing a magnetization state of a magnetic specimen of desired thickness with high resolution.
BACKGROUND ART
As techniques of observing a magnetization state of a magnetic specimen by means of an electron microscope, a method for detection of Lorentz deflection of an electron beam transmitting through the specimen (Lorentz electron microscope) or a method for detection of spin polarization of secondary electrons (spin polarization SEM) has been used. Of them, the Lorentz electron microscope is described in, for example, Surface Science, Vol. 13, pp. 525-532 (1992) and the spin polarization SEM is also described in Surface Science, Vol. 13, pp. 512-527 (1992).
DISCLOSURE OF INVENTION
Of the above prior arts, the Lorentz electron microscope faces a technical problem that before observation of the specimen, the specimen must be formed in advance into a film thin enough for an electron beam to transmit therethrough. Lorentz deflection of reflection electrons and secondary electrons can be detected (the magnetization state can be observed) without forming the specimen into a thin film but in that case, the change of detection signal due to Lorentz deflection becomes slight, raising a technical problem that full play cannot be given to high spatial resolution inherently owned by the electron microscope.
On the other hand, the aforementioned spin polarization SEM can afford to observe the magnetization state with high resolution without forming the specimen into a thin film but there needs special electron optical system and detector for detection of spin polarization of secondary electrons, raising a technical problem that the apparatus is inevitably complicated and increased in scale. In addition, the signal is sensitive to the surface condition of the specimen, also raising a technical problem that the function of applying the surface cleaning process to the specimen and a vacuum evacuation unit of high performance for maintaining the cleaned surface condition during observation are needed.
The present invention is made to solve the above-described problems and it is an object of the present invention to provide an electron microscope which can perform high-resolution observation of a magnetization state of a specimen without applying the complicated process of thin film forming and surface cleaning to the specimen and which can be simplified in equipment construction.
To accomplish the above object, in the present invention, in place of the electron detecting method of prior art, circularly polarized light, that is, light (an electromagnetic wave) having a polarization plane which rotates about an axis in the propagating direction, generated from an electron beam irradiated part of a specimen, especially, a magnetic specimen is detected. More specifically, an electron microscope comprises means for holding a specimen, means for irradiating an electron beam on the specimen (usually including an electron source and an electron optical system), and means for detecting an electromagnetic wave of circular polarization (so-called circularly polarized light) generated especially from an electron beam irradiated part of the specimen. Preferably, the circularly polarized light detecting means is provided between the specimen holding means (for example, a specimen holder) and the electron optical system of the electron beam irradiating means. Preferably, a power supply for applying a voltage between the specimen (or specimen holding means) and the electron optical system is provided.
In order to increase the generation efficiency of the circularly polarized light, energy of the irradiating electron beam is made to be low, preferably, 100 eV or less. Accordingly, in addition to the function of irradiating an electron beam on a desired part of a specimen as in the ordinary electron microscope, the presen
REFERENCES:
patent: 4440475 (1984-04-01), Colliaux
patent: 4900932 (1990-02-01), Schafer et al.
Surface Science, vol. 13, No. 9, "Spin-Polarized Scanning Electron Microscope", K. Hayakawa, pp. 512-517, Aug. 3, 1992.
Kuroda Katsuhiro
Suzuki Hiroshi
Takahashi Yoshio
Yajima Yusuke
Hitachi , Ltd.
Nguyen Kiet T.
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