Interference optical system unit, charged particle beam interference apparatus, and method for observing charged particle beam interference image

A charged particle beam interference apparatus comprising:

• a light source of a charged particle beam;
• an irradiation optical system that irradiates a specimen with the charged particle beam emitted from the light source of the charged particle beam;
• an objective lens system that includes at least one electromagnetic lens to form an image of the specimen;
• an imaging optical system that includes at least two electromagnetic lenses to magnify and form or demagnify and form the image of the specimen formed by the objective lens system;
• an interference optical system that forms an interference image from the image of the specimen formed by the imaging optical system;
• and
• a detection recorder that detects and records the interference image of the specimen,
• wherein, in an order along a flow direction of the charged particle beam, the light source of the charged particle beam, the irradiation optical system, the objective lens system, the imaging optical system, the interference optical system, and the detection recorder are disposed in said order along the flow direction of the charged particle beam,
• wherein the interference optical system includes at least one electromagnetic lens that forms an image of a charged particle beam, and at least one charged particle beam biprism,
• wherein the at least one electromagnetic lens of the interference optical system, the charged particle beam biprism, and a space to an image plane of the electromagnetic lens of the interference optical system are integrally configured as one unit, and
• wherein a magnification of the interference image of the specimen is changed by the electromagnetic lens included in the imaging optical system disposed upstream with respect to the interference optical system.

A method for observing a charged particle beam interference image using a charged particle beam interference apparatus, the method comprising:

• irradiating a specimen, using an irradiation optical system, with a charged particle beam emitted from a light source of the charged particle beam;
• forming an image of the specimen using an objective lens system that includes at least one electromagnetic lens;
• magnifying and forming, or demagnifying and forming, the image of the specimen formed by the objective lens using an imaging optical system that includes at least two electromagnetic lenses;
• forming an interference image from the image of the specimen formed by the imaging optical system suing an interference optical system;
• and
• detecting and recording the interference image of the specimen using a detection recorder,
• wherein, in an order along a flow direction of the charged particle beam, the light source of the charged particle beam, the irradiation optical system, the objective lens system, the imaging optical system, the interference optical system, and the detection recorder are disposed in said order along the flow direction of the charged particle beam,
• wherein an imaging condition of the interference optical system is kept to a preliminarily fixed constant condition, and
• wherein a setting and a change of an imaging magnification of the specimen is performed using the electromagnetic lens included in the imaging optical system disposed on an upstream side of the interference optical system excluding the interference optical system.