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

• US 6,333,510 B1
• Filed: 08/21/2000
• Issued: 12/25/2001
• Est. Priority Date: 08/11/1997
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Watanabe, Masahiro, Hiroi, Takashi, Tanaka, Maki, Usami, Yasutsugu, Shinada, Hiroyuki
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US09/642,014
• Time in Patent Office: 491 Days
• Field of Search: 250/559.3, 250/559.45, 250/559.4, 250/559.29, 250/492.3, 250/492.1, 250/397, 250/399, 250/559.27, 356/375, 356/376, 356/381
• US Class Current: 250/559.27
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01J 2237/20235 Z movement or adjustment
• CPC Class Codes: H01J 2237/20292 Means for position and/or orientation registration
• CPC Class Codes: H01J 2237/216 Automatic focusing methods
• CPC Class Codes: H01J 2237/2445 Photon detectors for X-rays, light, e.g. photomultipliers
• CPC Class Codes: H01J 2237/24578 Spatial variables, e.g. position, distance
• CPC Class Codes: H01J 2237/2482 Optical means
• CPC Class Codes: H01J 2237/2487 using digital signal processors
• CPC Class Codes: H01J 2237/2814 Measurement of surface topography
• CPC Class Codes: H01J 2237/2817 Pattern inspection
• CPC Class Codes: H01J 2237/2826 Calibration for object processing apparatus H01J2237/30433
• CPC Class Codes: H01J 2237/304 Controlling tubes
• CPC Class Codes: H01J 2237/3175 Lithography
• CPC Class Codes: H01J 37/20 Means for supporting or positioning the objects or the material; Means for adjusting diaphragms or lenses associated with the support introducing the objects H01J37/18
• CPC Class Codes: H01J 37/21 Means for adjusting the focus adjusting the focus while observing the image by photographic or optical means H01J37/22; means for observing the object or the point of impact on the object in tubes for the localised treatment of materials H01J37/3005
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube image data processing or generation, in general G06T
• CPC Class Codes: H01J 37/226 Optical arrangements for illuminating the object; optical arrangements for collecting light from the object
• CPC Class Codes: H01J 37/265 Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination
• CPC Class Codes: H01J 37/28 with scanning beams H01J37/268, H01J37/292, H01J37/2955 take precedence
• CPC Class Codes: H01J 37/304 : Controlling tubes by information coming from the objects or from the beam, e.g. correction signals
• CPC Class Codes: H01J 37/3174 : Particle-beam lithography, e.g. electron beam lithography

Abstract

An electron beam apparatus and method for at least obtaining an image of a specimen. The apparatus includes an electron optical system having 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 the specimen and a detector for detecting a secondary electron emanated from the specimen by irradiation of the electron beams. The apparatus further includes 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 on the surface of the specimen and outputting information of a position of the image of the light pattern, and 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. A focus controller is provided 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.

Claims

1. 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; 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.

2. An electron beam apparatus according to claim 1, wherein the detection optical system includes a linear sensor on which the image of the light pattern is projected.

3. 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.

4. A method according to claim 3, further comprising a step of detecting a defect on the surface of the specimen by using the obtained image.

6. A method according to claim 4, wherein the information displayed on a monitor screen is information of defects on the surface of the specimen.

5. 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.

7. 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.

8. An electron beam apparatus according to claim 7, wherein the detection optical system includes a linear sensor on which the image of the light pattern is projected.

9. 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.

10. A method according to claim 9, further comprising a step of detecting a defect on the surface of the specimen by using the obtained image.

11. 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.

12. A method according to claim 11, wherein the information displayed on a monitor screen is information of defects on the surface of the specimen.