Radiant energy – Inspection of solids or liquids by charged particles – Analyte supports
Patent
1982-02-03
1984-01-10
Smith, Alfred E.
Radiant energy
Inspection of solids or liquids by charged particles
Analyte supports
H01J 3720
Patent
active
044255071
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to devices for investigating surfaces of specimens with the aid of electron probes and, more particularly, to specimen chambers of electron probe instruments.
Still more specifically, the invention relates to a mechanism for moving a specimen inside a specimen chamber of an electron probe instrument.
BACKGROUND OF THE INVENTION
Electron probe instruments, such as projection and scanning electron microscopes and X-ray microanalyzers, are used for morphological investigation of the surface of solid specimens and for ultimate X-ray analysis of such specimens. While using a scanning electron microscope to investigate a specimen with a complicated surface structure, for example, a specimen with microcracks, it is necessary to make frequent and rapid changes of magnification. At first the investigator uses a small magnification to observe a large portion of the specimen's surface and select an area to be investigated. When this is done the specimen is brought to a different position corresponding to a greater magnification, which makes it possible to investigate the selected area of the specimen with a sufficiently high resolution. The possibility of making rapid and frequent changes of magnification is extremely important. For example, a small magnification is used to pinpoint defects of integrated microcircuits, whereas a great magnification is required to find the cause the microcracks on their surface. In view of the above considerations, the present invention is aimed at speeding up and facilitating the investigation of specimens with the aid of electron probe instruments.
There is known a specimen chamber of an electron probe instrument (cf. accepted Japanese Application No. 49-33903 published Sept. 10, 1974), comprising an airtight housing which accommodates an object stage for a specimen, and drive mechanisms for driving the object stage along three mutually perpendicular coordinate axes one of which is coincident with the electron-optical axis of the instrument; the drive mechanisms also serve to incline the object stage in relation to the electron-optical axis of the instrument and rotate the object stage about that axis.
The drive mechanism for moving the object stage along the electron-optical axis comprises a carriage which is a movable plate connected through an airtight sealing element to the side wall of the specimen chamber and driven by a screw rotatable in a stationary nut rigidly attached to the housing. The plate is provided with a hole through which extends a column of coaxial hollow shafts which serve to move the object stage along two more coordinate axes, as well as to incline the stage in relation to the electron-optical axis and rotate it about that axis. The external shaft of the column serves to incline the stage with respect to the electron-optical axis. Rigidly secured to the end of this external shaft is a bracket carrying a mechanism which contains profiled strips along which the object stage can be driven in a desired direction. This mechanism rests on a second column of coaxial shafts which is connected to the first column through a third column of coaxial shafts whose shafts are coupled to those of the first and second columns by means of conical and cylindrical gears.
The specimen chamber under review is disadvantageous in that it does not allow a rapid change of magnification within a sufficiently broad range with a preselected constant scanning angle of the electron probe. The screw gauge of the mechanism for driving the object stage along the electron-optical axis is controlled manually and thus does not allow a rapid change of the stage's position. Hence it takes too much time to vary the magnification.
The specimen chamber under review is also disadvantageous in that the drive mechanism for driving the object stage along the electron-optical axis drives not only the object stage, but also a portion of the chamber's housing and elements of the other drive mechanisms. Considering the total mass to be set in motion, i
REFERENCES:
patent: 4272682 (1981-06-01), Swann
Makarov Kirill A.
Morozov Vladimir I.
Panov Anatoly F.
Rudnev Alexandr V.
Grigsby T. N.
Schaffer Murray
Smith Alfred E.
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