Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Patent
1987-10-30
1989-04-04
Anderson, Bruce C.
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
2502521, H01J 37256
Patent
active
048188735
ABSTRACT:
The present invention relates to an apparatus for calibrating the magnification of a scanning electron microscope. The microscope includes a generator for generating an electron beam, a scanning signal generator for producing a scanning signal and a unit for scanning the beam. The apparatus is comprised of a calibration object which has a plurality of aligned elements thereon which, when scanned by the electron beam produces a signal having a frequency which has a fundamental periodicity dependent on the spacing of the aligned elements. A detector is provided for detecting the signal and producing an output signal having a data content and the fundamental periodicity. A unit is connected to the detector for determining the fundamental periodicity of the output signal from the entire data content of the output signal. A control unit is provided for producing a desired magnification signal. A generator is connected to the unit for determining the fundamental periodicity of the output signal and to the control unit for producing a correction signal which is derived from the desired magnification signal and the fundamental periodicity of the output signal. A combiner is connected to the generator and the unit for scanning the beam for combining the correction signal and the scanning signal to produce a modified scanning signal which scans the electron beam to produce the desired magnification of the scanning electron microscope.
REFERENCES:
patent: 3156820 (1964-11-01), Reimer
patent: 3757117 (1973-09-01), Muller et al.
patent: 4068381 (1978-01-01), Ballard
patent: 4677296 (1987-06-01), Lischke et al.
Seiler et al., SPIE, vol. 480, Integrated Circuit Metrology II, (1984), pp. 86-93.
National Bureau of Standards Certificate, Standard Reference Material 484d; Jul. 22, 1985.
Anderson Bruce C.
Baker John A.
Berman Jack I.
Vickers Instruments (Canada) Inc.
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