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US 7,126,120 B2Granted
Electron microscope
AssigneeHitachi High-Technologies Corporation
InventorHiromi Inada
Life of this patent
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Abstract
In an electron microscope, focus correction is carried out automatically, an astigmatic difference amount is displayed and astigmatism correction is executed quantitatively. Enlarged specimen images obtained by irradiating an electron beam on a specimen while changing excitation currents of an objective lens and of a stigmator coil are picked up by a capturing unit comprised of an optical lens and a capturing device and image sharpness coefficients are calculated by means of an arithmetic logic unit. A suitable astigmatism correction direction is chosen on the basis of an angular component value of the obtained image sharpness coefficients and then, a correction excitation current is supplied to a stigmator coil to correct astigmatism and a correction excitation current is supplied to an objective lens coil to perform focus correction.
Claims16
A specimen observing method based on an electron microscope, comprising:
- a step of picking up enlarged specimen images by changing focal position of an electron beam in relation to a specimen;
- a step of image-calculating image sharpness coefficients of the enlarged specimen images;
- and
- a step of deciding the number of peaks on a curve indicative of the relation between focal position of the electron beam and image sharpness coefficient,
- wherein when two peaks are determined to exist in said decision, an astigmatism correction process proceeds, said astigmatism correction process including:
- a step of picking up enlarged specimen images by changing astigmatism correction current of a stigmator in X direction;
- a step of image-calculating image sharpness coefficients of the enlarged specimen images;
- a step of determining a minimum position sandwiched by two peaks on a curve indicative of the relation between the astigmatism correction current of said stigmator in X direction and the image sharpness coefficient;
- a step of setting the astigmatism correction current of said stigmator in X direction to a current value corresponding to said minimum position;
- a step of picking up enlarged specimen images by changing astigmatism correction current of a stigmator in Y direction;
- a step of image-calculating image sharpness coefficients of the enlarged specimen images;
- a step of determining a minimum position sandwiched by two peaks on a curve indicative of the relation between astigmatism correction current of said stigmator in Y direction and image sharpness coefficient;
- and
- a step of setting the astigmatism correction current of said stigmator in Y direction to a current value corresponding to said minimum position.
11 more elements
A specimen observing method based on an electron microscope, comprising:
- a step of picking up enlarged specimen images by changing focal position of an electron beam in relation to a specimen;
- a step of image-calculating an angular direction component of image sharpness coefficient of the enlarged specimen image;
- a step of deciding an astigmatism correction direction from a result of the calculation of the angular direction component of image sharpness coefficient of said enlarged specimen image;
- a step of picking up enlarged specimen images by changing the astigmatism correction current of stigmator in said determined direction;
- a step of calculating image sharpness coefficients of said enlarged specimen images;
- a step of determining a minimum position sandwiched by two peaks on a curve indicative of the relation between astigmatism correction current of said stigmator and image sharpness coefficient;
- and
- a step of setting the astigmatism correction current of said stigmator to a current value corresponding to said minimum position.
5 more elements
An electron beam apparatus for observing a specimen, the apparatus comprising:
- an electron microscope for irradiating the specimen with an electron beam and generating enlarged images of the specimen from the electron beam irradiation of the specimen, the electron microscope including a stigmator;
- and
- a controller for controlling operation of the electron microscope, configured to cause the electron microscope to implement steps comprising:
- picking up enlarged specimen images by changing focal position of the electron beam in relation to a specimen;
- image-calculating image sharpness coefficients of the enlarged specimen images;
- and
- deciding the number of peaks on a curve indicative of the relation between focal position of the electron beam and image sharpness coefficient, wherein when two peaks are determined to exist in said decision, an astigmatism correction process proceeds, said astigmatism correction process including:
- picking up enlarged specimen images by changing astigmatism correction current of the stigmator in X direction;
- image-calculating image sharpness coefficients of the enlarged specimen images;
- determining a minimum position sandwiched by two peaks on a curve indicative of the relation between the astigmatism correction current of the stiginator in the X direction and the image sharpness coefficient;
- setting the astigmatism correction current of the stigmator in the X direction to a current value corresponding to said minimum position;
- picking up enlarged specimen images by changing astigmatism correction current of the stigmator in Y direction;
- image-calculating image sharpness coefficients of the enlarged specimen images;
- determining a minimum position sandwiched by two peaks on a curve indicative of the relation between astigmatism correction current of the stigmator in the Y direction and image sharpness coefficient;
- and
- setting the astigmatism correction current of the stigmator in the Y direction to a current value corresponding to said minimum position.
13 more elements
An electron beam apparatus for observing a specimen, the apparatus comprising:
- an electron microscope for irradiating the specimen with an electron beam and generating enlarged images of the specimen from the electron beam irradiation of the specimen, the electron microscope including a stigmator;
- and
- a controller for controlling operation of the electron microscope, configured to cause the electron microscope to implement steps comprising:
- picking up enlarged specimen images by changing focal position of the electron beam in relation to a specimen;
- image-calculating an angular direction component of image sharpness coefficient of the enlarged specimen images;
- deciding an astigmatism correction direction from a result of the calculation of the angular direction component of image sharpness coefficient of said enlarged specimen images;
- picking up enlarged specimen images by changing the astigmatism correction current of the stigmator in said determined direction;
- calculating image sharpness coefficients of said enlarged specimen images;
- determining a minimum position sandwiched by two peaks on a curve indicative of the relation between astigmatism correction current of the stigmator and image sharpness coefficient;
- and
- setting the astigmatism correction current of the stigmator to a current value corresponding to said minimum position.
8 more elements
Dependencies are inferred from the claim text.