Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2000-08-21
2001-12-25
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S559290
Reexamination Certificate
active
06333510
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam exposure or system inspection or measurement or processing apparatus having an observation function using charged particle beams such as electron beams or ion beams and its method and an optical height detection apparatus.
Heretofore, a focus of an electron microscope has been adjusted by adjusting a control current of an objective lens while an electron beam image is observed. This process requires a lot of time, and also, a sample surface is scanned by electron beams many times. Accordingly, there is the possibility that a sample will be damaged.
In order to solve the above-mentioned problem, in a prior-art technique (Japanese laid-open patent application No. 5-258703), there is known a method in which a control current of an optimum objective lens relative to a height of a sample surface in several samples are measured in advance before the inspection is started and focuses of respective points are adjusted by interpolating these data when samples are inspected.
In this method, SEM images obtained by changing an objective lens control current at every measurement point are processed, and an objective lens control current by which an image of a highest sharpness is recorded. It takes a lot of time to measure an optimum control current before inspection. Moreover, there is the risk that a sample will be damaged due to the irradiation of electron beams for a long time. Further, there is the problem that a height of a sample surface will be changed depending upon a method of holding a wafer during the inspection.
Moreover, as the prior-art technique of the apparatus for inspecting a height of a sample, there are known Japanese laid-open patent application No. 58-168906 and Japanese laid-open patent application No. 61-74338.
According to the above-mentioned prior art, in the electron beam apparatus, the point in which a clear SEM image without image distortion is detected and a defect of a very small pattern formed on the inspected object like a semiconductor wafer such as ULSI or VLSI is inspected and a dimension of a very small pattern is measured with high accuracy and with high reliability has not been considered sufficiently.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention is to provide an electron beam exposure or system inspection or measurement apparatus and a method thereof in which the image distortion caused by the deflection and the aberration of the electron optical system can be reduced, the decrease of the resolution due to the de-focusing can be reduced so that the quality of the electron beam image (SEM image) can be improved and in which the inspection and the measurement of length based on the electron beam image (SEM image) can be executed with high accuracy and with high reliability.
It is another object of the present invention is to provide an electron beam exposure or system inspection or measurement apparatus and a method thereof in which the height of the surface of the inspected object can be detected real time and the electron optical system can be controlled real time so that an electron beam image (SEM image) of high resolution without image distortion can be obtained by the continuous movement of the stage, an inspection efficiency and its stability can be improved and in which an inspection time can be reduced.
It is a further object of the present invention to provide an electron beam exposure apparatus and a converging ion beam manufacturing apparatus in which very small patterns can be exposed and manufactured without image distortion and with a high resolution.
In order to attain the above-mentioned objects, according to the present invention, there is provided an electron beam system inspection or measurement apparatus which is comprised of a detection apparatus including an electron optical system comprising an electron beam source, a deflection element for deflecting electron beams emitted from the electron beam source, and an objective lens for converging and irradiating electron beams deflected by the deflection element on an inspected object, an electron beam image detection optical system for detecting a secondary electron beam image generated from the inspected object by the electron beams deflected by the electron optical system and converged and irradiated, a projection optical system for projecting a luminous flux of a repetitive light pattern or lattice shape on the inspected object from the oblique upper direction of the inspected object and a detection optical system for detecting the position of an optical image by focusing the luminous flux of the repetitive light pattern which was reflected on the surface of the inspected object by the luminous flux of the repetitive light pattern projected by the projection optical system, an optical height detection apparatus arranged so as to optically detect a height of the surface in an area on the inspected object based on the change of the position of an optical image composed of a luminous flux of the repetitive light pattern detected by the detection optical system, a focus controller for focusing electron beams on the inspected object in a properly-focused state by controlling a current flowed to or a voltage applied to an objective lens of the electron optical system on the basis of the height of the surface on the inspected object detected by the optical height detection apparatus and an image processor for inspecting or measuring a pattern formed on the inspected object on the basis of the secondary electron beam image detected by the electron beam image detection optical system.
In accordance with the present invention, there is provided an electron beam apparatus comprising a pattern writing apparatus including an electron optical system comprising an electron beam source, a deflection element for deflecting electron beams emitted from the electron beam source, and an objective lens for converging and irradiating electron beams deflected by deflection element on a processed object, a projection optical system for projecting a luminous flux a repetitive light pattern on the processed object from an oblique upper direction of the processed object and a detection optical system for detecting the position of an optical image by focusing the luminous flux of the repetitive light pattern which was reflected on a surface of the processed object by the luminous flux of the repetitive light pattern projected by the projection optical system, an optical height detection apparatus arranged so as to optically detect a height of the surface in an area on the processed object based on the change of the position of an optical image composed of the luminous flux of the repetitive light pattern detected by the detection optical system, and a focus controller for focusing electron beams on the processed object in a properly-focused state by controlling a current flowed to or a voltage applied to the objective lens of the electron optical system on the basis of the height of the surface on the inspected object detected by the optical height detection apparatus.
Further, according to the another feature present invention, there is provided an electron beam system inspection or measurement apparatus which is comprised of a detection apparatus including an electron optical system comprising an electron beam source, a deflection element for deflecting electron beams emitted from the electron beam source, and an objective lens for converging and irradiating electron beams deflected by the deflection element on an inspected object, an electron beam image detection optical system for detecting a secondary electron beam image generated from the inspected object by the electron beams deflected by the electron optical system and converged and irradiated, an optical height detection apparatus for optically detecting a height of a surface in an area on the inspected object irradiated by electron beams deflected and converged by the electron optical system, a focus controller for focusing electron beams o
Hiroi Takashi
Shinada Hiroyuki
Tanaka Maki
Usami Yasutsugu
Watanabe Masahiro
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Le Que T.
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