Electron beam exposure or system inspection of measurement apparatus and its method and height detection apparatus

A method of obtaining an image of a specimen, comprising the steps of:

• projecting a light pattern onto a surface of a specimen from an oblique direction to the surface onto which an electron beam is converged and irradiated through an objective lens;
• detecting an image of the light pattern projected onto the surface of the specimen with a sensor;
• outputting information of a position of the image of the light pattern on the sensor;
• calculating height of the surface of the specimen by using the information of the position of the image;
• controlling the objective lens in accordance with the calculated height information to focus the electron beam onto the surface of the specimen;
• and
• obtaining an image of the surface of the specimen by detecting a secondary electron emanated from the surface by the irradiation of the electron beam focused on the surface.

A method of detecting a secondary electron image, comprising the steps of:

• irradiating and deflecting a converged electron beam onto a surface of a specimen through an objective lens;
• projecting a light pattern onto the surface of the specimen from an oblique direction to the surface including a portion of the surface where a light axis of the objective lens impinges;
• detecting an image of the light pattern projected onto the surface of the specimen with a sensor;
• calculating height of the surface of the specimen by using the information of the detected image;
• focusing the electron beam onto the surface of the specimen by controlling the objective lens in accordance with the calculated height information;
• detecting a secondary electron emanated from the surface by the irradiation of the electron beam focused on the surface;
• and
• displaying information of the surface of the specimen on a monitor screen in accordance with the detected secondary electron.

An electron beam apparatus, comprising:

• an electron optical system including an electron beam source, an element for deflecting electron beams emitted from the electron beam source, an objective lens for converting and irradiating electron beams deflected by the deflection element onto a specimen and a detector for detecting a secondary electron emanated from the specimen by irradiation of the electron beams;
• a projection optical system for projecting a light pattern onto a surface of the specimen in the vicinity of a beam axis of the electron optical system from an oblique direction to the surface;
• a detection optical system for detecting an image of the light pattern projected onto the surface of the specimen and outputting information of a position of the image of the light pattern;
• a surface height detection unit for outputting height information of the surface of the specimen by using the output information from the detection optical system;
• an offset compensator which compensates an offset of the detected surface height;
• and
• a focus controller for focusing the electron beam onto the surface of the specimen by controlling the objective lens of the electron optical system in accordance with the height information from the surface height detection unit.

A method of obtaining an image of a specimen, comprising the steps of:

• projecting a light pattern onto a surface of a specimen from an oblique direction to the surface onto which an electron beam is converged and irradiated through an objective lens;
• detecting an image of the light pattern projected onto the surface of the specimen with a sensor;
• outputting information of a position of the image of the light pattern on the sensor;
• calculating height of the surface of the specimen by using the information of the position of the image;
• controlling the objective lens in accordance with the calculated height information to focus the electron beam onto the surface of the specimen;
• compensating an offset of the calculated height of the surface of the specimen;
• and
• obtaining an image of the surface of the specimen by detecting a secondary electron emanated from the surface by the irradiation of the electron beam focused on the surface.

A method of detecting a secondary electron image, comprising the steps of:

• irradiating and deflecting a converged electron beam onto a surface of a specimen through an objective lens;
• projecting a light pattern onto the surface of the specimen from an oblique direction to the surface including a portion of the surface where a light axis of the objective lens impinges;
• detecting an image of the light pattern projected onto the surface of the specimen with a sensor;
• calculating height of the surface of the specimen by using the information of the detected image;
• focusing the electron beam onto the surface of the specimen by controlling the objective lens in accordance with the calculated height information;
• detecting a secondary electron emanated from the surface by the irradiation of the electron beam focused on the surface;
• compensating an offset of the calculated height of the surface of the specimen;
• and
• displaying information of the surface of the specimen on a monitor screen in accordance with the detected secondary electron.