Electron beam device including a first electron biprism to split an electron beam into two beams and a second electron biprism in the image forming lens system to superpose the two beams

An electron beam device provided with an electron biprism including a pair of parallel plate ground electrodes having an optical axis interposed therebetween, and an electrode filament provided in a center part of the parallel flat electrodes while perpendicularly intersecting the optical axis, comprising:

• an electron source;
• an acceleration tube that brings an electron emitted from the electron source into an electron beam at a predetermined velocity;
• an irradiation lens system that irradiates a specimen with the electron beam;
• a specimen holder that holds the specimen;
• an objective lens system that includes at least one electron lens for forming an image of the specimen;
• an image forming lens system that forms the image of the specimen, which has been formed by the objective lens system;
• an observation plane for observation of the specimen image formed by the image forming lens system;
• an observation recording system for observing or recording the specimen image formed on the observation plane;
• a first electron biprism provided in the irradiation lens system for splitting the electron beam into a first electron beam and a second electron beam;
• and
• at least one electron biprism provided in the image forming lens system for superposing the first electron beam and the second electron beam on the observation plane, wherein:
• an optical action of the irradiation lens system controls each current density of the first electron beam and the second electron beam on the objective plane of the objective lens system where the specimen exists, and a distance on electron optics between the first electron biprism and the objective plane of the objective lens system where the specimen exists;
• and
• the optical action of the irradiation lens system satisfies a formula (3) or (4)
• [Formula 6]
• β1<λ/2d1 (3)
• [Formula 7]
• Lc1>d1 (4)
• where λ denotes a wavelength of the electron beam, Lc1 denotes a coherence distance of the electron beam on a plane of the electrode filament of the first electron biprism on the electron optics, β1 denotes an opening angle of the electron beam emitted from the electron source on the electron optics with respect to the first electrode filament plane on the electron optics, and d1 denotes a diameter of the electrode filament of the first electron biprism on the electron optics.

An electron beam device comprising:

• an electron source;
• an acceleration tube that brings an electron emitted from the electron source into an electron beam at a predetermined velocity;
• an irradiation lens system that includes at least one electron lens for irradiating a specimen with the electron beam;
• a specimen holder that holds the specimen;
• an objective lens system that includes at least one electron lens for forming an image of the specimen;
• an image forming lens system that forms the image of the specimen, which has been formed by the objective lens system;
• an observation plane for observation of the specimen image formed by the image forming lens system;
• an observation recording system for observing or recording the specimen image formed on the observation plane;
• a first electron biprism provided between the irradiation lens system and the specimen for splitting the electron beam into a first electron beam that transmits through the specimen and a second electron beam that does not transmit through the specimen;
• and
• at least one electron biprism provided in the image forming lens system for superposing the first electron beam and the second electron beam on the observation plane, wherein:
• an optical action of the irradiation lens system controls each current density of the first electron beam and the second electron beam on the objective plane of the objective lens system where the specimen exists, and a distance on electron optics between the electron source when the image is formed by the irradiation lens system and the objective plane of the objective lens system where the specimen exists;
• a distance between the first electron biprism and the objective plane of the objective lens system where the specimen exists on electron optics is controlled so that the first electron beam and the second electron beam are radiated to a first region and a second region differently positioned on the objective plane of the objective lens system where the specimen exists;
• and
• the superposed region of the first electron beam and the second electron beam on the observation plane is observed or recorded by the observation recording system.