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

• US 20020053634A1
• Filed: 12/12/2001
• Published: 05/09/2002
• Est. Priority Date: 08/11/1997
• Status: Active Grant

• Current Assignee: Hiroyuki Shinada, Maki Tanaka, Masahiro Watanabe, Takashi Hiroi, Yasutsugu Usami
• Original Assignee: Hiroyuki Shinada, Maki Tanaka, Masahiro Watanabe, Takashi Hiroi, Yasutsugu Usami
• Inventors: Watanabe, Masahiro, Hiroi, Takashi, Tanaka, Maki, Usami, Yasutsugu, Shinada, Hiroyuki
• Granted Patent: US 6,753,518 B2
• Time in Patent Office: Days
• US Class Current: 250/201.2
• 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
• 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 object or the material; Means for adjusting diaphragms or lenses associated with the support
• CPC Class Codes: H01J 37/21 Means for adjusting the focus
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube
• 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 includes a movable table which mounts a specimen, an electron optical system including an electron beam source which emits electron beams, an element for deflecting the emitted electron beams, an objective lens for converging and irradiating the deflected electron beams onto the specimen mounted on the table, and a detector for detecting a secondary electron emanated from the specimen by the irradiation of the electron beams. A surface height detection unit is provided which optically detects a height of a surface of the specimen by projecting light onto the surface of the specimen from an oblique direction to the surface and detecting light reflected from the specimen. A focus controller is provided for focusing the electron beam onto the surface of the specimen by controlling a position of the table in a height direction in accordance with the height information from the surface height detection unit.

Claims

1. An electron beam apparatus, comprising:

a table which mounts a specimen and is movable in three dimensional directions;

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 converging and irradiating electron beams deflected by the deflection element onto a specimen mounted on the table and a detector for detecting a secondary electron emanated from the specimen by the irradiation of the electron beams;

a surface height detection unit which optically detects a height of a surface of the specimen by projecting light onto the surface of the specimen from an oblique direction to the surface and detecting light reflected from the specimen; and

a focus controller which focuses the electron beam onto the surface of the specimen by controlling a position of the table in a height direction in accordance with information of the height from the surface height detection unit.

2. An electron beam apparatus according to claim 1, wherein the surface height detection unit projects a repetitive light pattern onto the surface of the specimen and detects light reflected from the specimen with a linear sensor.

3. An electron beam apparatus according to claim 1, further comprising an image data processing unit which receives secondary electron image data from the detector of the electron optical system and processes the received image data.

4. An electron beam apparatus according to claim 3, further comprising a display unit which displays a secondary electron image of the surface of the specimen outputted from the image data processing unit.

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

irradiating an electron beam onto a specimen set on a table;

optically detecting height of a surface of the specimen set on the table by projecting light onto the surface of the specimen from an oblique direction to the surface and detecting light reflected from the specimen;

focusing the electron beam onto the surface of the specimen by controlling a position of the table in a height direction in accordance with the optically detected height information;

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; and

outputting information of a secondary electron image of the surface of the specimen obtained by the obtaining step.

6. A method according to claim 5, wherein the step of outputting includes displaying the secondary electron image on a monitor screen.

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

setting a specimen on a table;

irradiating an electron beam on a specimen set on the table;

optically detecting a height of a surface of the specimen set on the table which moves in a predetermined direction by projecting light onto the surface of the specimen from an oblique direction to the surface and detecting light reflected from the specimen;

focusing the electron beam onto the surface of the specimen by controlling a position of the table in a height direction in accordance with information of the optically detected height;

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; and

processing the obtained image and outputting the processed image.

8. A method according to claim 7, further comprising a step of displaying a secondary electron image of the surface of the specimen obtained by the obtaining step on a monitor screen.

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

irradiating an electron beam on a specimen set on a table;

optically detecting a height of a surface of a specimen set on the table;

focusing the electron beam onto the surface of the specimen by controlling a relative position of a height direction between a focus position of an electron optical system from which the electron beam is irradiated and the table in accordance with information of the optically detected height;

obtaining an image of the surface of the specimen by detecting a secondary electron emanated from the surface of the specimen by the irradiation of the electron beam focused on the surface;

processing the obtained image; and

displaying a processed information on a monitor screen.

10. A method according to claim 9, wherein the table continuously moves at least in one direction while optically detecting height of the surface of the specimen set on the table.

11. A method according to claim 9, wherein the focusing the electron beam onto the surface of the specimen is conducted by controlling a position of the table in a height direction in accordance with the optically detected height information.

12. A method according to claim 9, wherein the processing includes inspection or measurement of the obtained image.

14. A method according to claim 13, wherein the step of optically detecting height of the surface of the specimen includes projecting a light pattern onto the surface of the specimen from an oblique direction to the surface and detecting a reflected light from the surface.

15. A method according to claim 13, wherein the step of processing includes comparing the obtained image with another obtained image to detect a defect.

16. A method according to claim 13, wherein the step of outputting information of the detected defect includes displaying an image of the detected defect on a monitor screen.

13. A method of inspecting a specimen, comprising the steps of:

irradiating an electron beam on a specimen set on a table;

optically detecting height of a surface of a specimen set on the table;

focusing the electron beam onto the surface of the specimen by controlling a relative position of a height direction between a focus position of an electron optical system from which the electron beam is irradiated and the table in accordance with information of the optically detected height;

obtaining an image of the surface of the specimen by detecting a secondary electron emanated from the surface of the specimen by the irradiation of the electron beam focused on the surface;

processing the obtained image to detect a defect of the specimen; and

outputting information of the detected defect on a monitor screen.