Scanning electron microscope
AssigneeHitachi High-Technologies Corporation
InventorsHirohiko Kitsuki, Kazuo Aoki, Mitsugu Sato
Life of this patent
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Abstract
A scanning electron microscope for digitally processing an image signal to secure the largest focal depth and the best resolution in accordance with the magnification for observation is disclosed. The angle of aperture of an optical system having a plurality of convergence lenses is changed by changing the convergence lenses and the hole diameter of a diaphragm. The angle α of aperture of the electron beam is changed in accordance with the visual field range corresponding to a single pixel, i.e. what is called the pixel size.
Claims20
A scanning electron microscope comprising:
- a sample holder for holding a sample;
- an electron beam source;
- a plurality of convergence leases for converging the electron beam emitted from the electron beam source;
- an objective lens for radiating the converged electron beam as a micro spot on the sample;
- a scanning coil for scanning the electron beam on the sample;
- a detector for detecting the sample signal generated from the sample irradiated with the electron beam;
- an analog-to-digital (A/D) converter for converting the analog detection signal of the detector to a digital signal;
- a storage unit for storing the digital signal converted by the A/D converter as an image signal;
- and
- a display unit for displaying an image associated with the image signal stored in the storage unit;
- wherein the A/D converter can change the number of pixels per screen to change the resolution of the image by changing the sampling rate, the number of pixels being directly related to the sampling rate, and
- wherein the angle of aperture of the electron beam is changed in accordance with the pixel size (visual field area per pixel) determined in accordance with the number of pixels per screen.
A scanning electron microscope comprising:
- a sample holder for holding a sample;
- an electron beam source;
- a plurality of convergence lenses for converging the electron bean emitted from the electron beam source;
- an objective lens for radiating the converged electron beam as a micro spot on the sample;
- a scanning coil for scanning the electron beam on the sample;
- a detector for detecting the sample signal generated from the sample irradiated with the electron beam;
- an analog-to-digital (A/D) converter for converting the analog detection signal of the detector to a digital signal;
- a storage unit for storing the digital signal converted by the A/D converter as an image signal;
- and
- a display unit for displaying an image associated with the image signal stored in the storage unit;
- wherein the A/D converter can change the number of pixels per screen by switching the sampling rate,
- wherein the angle of aperture of the electron beam is changed in accordance with the pixel size (visual field area per pixel) determined in accordance with the number of pixels per screen, and
- wherein the angle of aperture of the electron beam is changed in accordance with the pixel size in a designated range, while the angle of aperture is set to a predetermined value regardless of the pixel size in other than the designated range.
A scanning electron microscope comprising:
- a sample holder for holding a sample;
- an electron beam source;
- a plurality of convergence lenses for converging the electron beam emitted from the electron beam source;
- an objective lens for radiating the converged electron beam as a micro spot on the sample;
- a scanning coil for scanning the electron beam on the sample;
- a detector for detecting the sample signal generated from the sample irradiated with the electron beam;
- an analog-to-digital (A/D) converter for converting the analog detection signal of the detector to a digital signal;
- a storage unit for storing the digital signal converted by the A/D converter as an image signal;
- and
- a display unit for displaying an image associated with the image signal stored in the storage unit;
- wherein the A/D converter can change the number of pixels per screen by switching the sampling rate,
- wherein the angle of aperture of the electron beam is changed in accordance with the pixel size (visual field area per pixel) determined in accordance with the number of pixels per screen, and
- wherein the angle of aperture of the electron beam is changed in accordance with the pixel size in a designated range, a first angle of aperture is set for the pixel size smaller than the designated pixel size and a second angle of aperture is set for the pixel size larger than the designated pixel size.
A scanning electron microscope for displaying an image based on signals generated from a sample when the sample is irradiated by an electron beam, comprising:
- an electron beam irradiation unit for irradiating an electron beam to the sample;
- a magnification setting unit for setting a magnification of the image;
- means for changing an angle of aperture of the electron beam incident on the sample according to the magnification set by the magnification setting unit;
- and
- an image display device for displaying an image based on the signals detected.
A scanning electron microscope for displaying on the screen an image of detected signals generated from a sample when the sample is irradiated with an electron beam, comprising:
- a magnification setting unit for setting a magnification of the electron beam;
- and
- means for changing the angle of aperture of the electron beam according to the magnification set by the magnification setting unit.
Dependencies are inferred from the claim text.