Charged-particle beam apparatus and method for automatically correcting astigmatism and for height detection
First Claim
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1. A charged-particle beam apparatus comprising:
- a stage on which a sample is set;
a charged-particle optical system for converging a charged-particle beam generated by a charged-particle source;
a scanning means for scanning an area on said sample in which a pattern is formed with said charged-particle beam converged by said charged-particle optical system;
a focus control means for controlling a focal position of said charged-particle beam converged by said charged-particle optical system;
an astigmatism adjustment means for adjusting astigmatism of said charged-particle beam converged by said charged-particle optical system;
an image detection means for obtaining an image of said sample by detecting secondary particles generated from said sample by the scanning of said converged charged-particle beam by said scanning means;
an image-processing means for processing said image obtained by said image detection means; and
a control system for adjusting and controlling said astigmatism of said converged charged-particle beam by using information from said image-processing means, wherein, said control system so controls that said scanning means scans said charged particle bean in one direction, said image detection means obtains plural images of said sample having mutually different focal positions by changing focal position of said charged particle beam with said focus control means, said image processing means computes sharpness values of said charged-particle optical system in two directions which are substantially perpendicular with each other, said scanning means changes scanning direction in another direction inclined to said one direction and scanning said area on said sample in a direction inclined to that of the previous scanning of said area, said image detection means obtains plural images of said sample having mutually different focal positions by changing focal position of said charged particle beam with said focus control means, said image processing means computes sharpness values of said charged-particle optical system in two directions which are substantially perpendicular with each other, calculating astigmatism of said charged-particle optical system based on said computed sharpness value in four directions of said converged charged-particle beam and feeding back an astigmatism correction amount to said astigmatism adjustment means based on said calculated astigmatism.
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Abstract
Charged-particle beam arrangements (e.g., apparatus and methods) for automatically correcting astigmatism and for height detection.
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Citations
34 Claims
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1. A charged-particle beam apparatus comprising:
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a stage on which a sample is set;
a charged-particle optical system for converging a charged-particle beam generated by a charged-particle source;
a scanning means for scanning an area on said sample in which a pattern is formed with said charged-particle beam converged by said charged-particle optical system;
a focus control means for controlling a focal position of said charged-particle beam converged by said charged-particle optical system;
an astigmatism adjustment means for adjusting astigmatism of said charged-particle beam converged by said charged-particle optical system;
an image detection means for obtaining an image of said sample by detecting secondary particles generated from said sample by the scanning of said converged charged-particle beam by said scanning means;
an image-processing means for processing said image obtained by said image detection means; and
a control system for adjusting and controlling said astigmatism of said converged charged-particle beam by using information from said image-processing means, wherein, said control system so controls that said scanning means scans said charged particle bean in one direction, said image detection means obtains plural images of said sample having mutually different focal positions by changing focal position of said charged particle beam with said focus control means, said image processing means computes sharpness values of said charged-particle optical system in two directions which are substantially perpendicular with each other, said scanning means changes scanning direction in another direction inclined to said one direction and scanning said area on said sample in a direction inclined to that of the previous scanning of said area, said image detection means obtains plural images of said sample having mutually different focal positions by changing focal position of said charged particle beam with said focus control means, said image processing means computes sharpness values of said charged-particle optical system in two directions which are substantially perpendicular with each other, calculating astigmatism of said charged-particle optical system based on said computed sharpness value in four directions of said converged charged-particle beam and feeding back an astigmatism correction amount to said astigmatism adjustment means based on said calculated astigmatism. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 26)
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17. A charged-particle beam apparatus comprising:
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a stage on which a sample is set;
a charged-particle optical system for converging a charged-particle beam generated by a charged-particle source;
a scanning means for scanning an area on said sample in which a pattern is formed with said charged-particle beam converged by said charged-particle optical system;
a focus control means for controlling a focal position of said charged-particle beam converged by said charged-particle optical system;
an astigmatism adjustment means for adjusting astigmatism of said charged-particle beam converged by said charged-particle optical system;
an image detection means for obtaining an image of said sample by detecting secondary particles generated from said sample by the scanning of said converged charged-particle beam by said scanning means;
an image-processing means for processing said image obtained by said image detection means;
a control system for adjusting and controlling said astigmatism of said converged charged-particle beam by using information from said image-processing means; and
a height detection means for optically detecting a height on an object substrate serving as said sample, wherein said control system so controls that said scanning means scans said charged particle bean in one direction, said image detection means obtains plural images of said sample having mutually different focal positions by changing focal position of said charged particle beam with said focus control means, said image processing means computes sharpness values of said charged-particle optical system in two directions which are substantially perpendicular with each other, said scanning means changes scanning direction in another direction inclined to said one direction and scanning said area on said sample in a direction inclined to that of the previous scanning of said area, said image detection means obtains plural images of said sample having mutually different focal positions by changing focal position of said charged particle beam with said focus control means, said image processing means computes sharpness values of said charged-particle optical system in two directions which are substantially perpendicular with each other, calculating astigmatism of said charged-particle optical system based on said computed sharpness value in four directions of said converged charged-particle beam and feeding back an astigmatism correction amount to said astigmatism adjustment means based on said calculated astigmatism, and wherein said focus control means is controlled on the basis of said optically detected height on said object substrate.
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18. A method for adjusting astigmatism of a charged-particle beam apparatus, comprising:
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converging a charged-particle beam, which is generated by a charged-particle source, by using a charged-particle optical system;
irradiating and scanning in one direction said converged charged-particle beam in an area on a sample, on which a pattern is formed, to obtain an image of said sample by detecting secondary particles generated from said sample by said irradiating and scanning said converged charged-particle beam;
changing a focal position of said converged charged-particle beam;
obtaining a plurality of images of said sample having mutually different focal positions by repeating the operations from converging to changing for plural times;
repeating the operations from converging to obtaining once more by changing said scanning direction of said converged charged-particle beam to be inclined to said one direction at the irradiating and scanning operations, thereby scanning said area on said sample in a direction inclined to that of the previous scanning of said area;
computing an astigmatism of said charged-particle optical system by calculating sharpness values in two directions substantially perpendicular with each other from the plurality of images obtained at said obtaining operation by scanning said converged charged-particle beam in said one direction and sharpness values in another two directions substantially perpendicular with each other from the plurality of images obtained at said obtaining operation by scanning said converged charged-particle beam in another direction inclined to said one direction and estimating an astigmatism correction amount from said calculated sharpness value in four directions; and
controlling and adjusting said astigmatism of said charged-particle optical system by feeding back said astigmatism correction amount based on said computed astigmatism. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 27)
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28. A method for adjusting astigmatism of a charged-particle beam apparatus, said method comprising:
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converging a charged-particle beam, which is generated by a charged-particle source, by using a charged-particle optical system;
irradiating and scanning in one direction said converged charged-particle beam in an area of a sample, on which a pattern is formed, to obtain an image of said sample by detecting secondary particles generated from said sample by said irradiating and scanning said converged charged-particle beam;
changing a focal position of said converged charged-particle beam;
obtaining a plurality of images of said sample having mutually different focal positions by repeating the operations from converging to changing for plural times;
repeating the operations from converging to obtaining once more by changing said scanning direction of said converged charged-particle bean to be inclined to said one direction at the irradiating and scanning operations, thereby scanning said area on said sample in a direction inclined to that of the previous scanning of said area;
computing an astigmatism of said charged-particle optical system by calculating sharpness values in two directions substantially perpendicular with each other from the plurality of images obtained at said obtaining operation by scanning said converged charged-particle beam in said one direction and sharpness values in another two directions substantially perpendicular with each other from the plurality of images obtained at said obtaining operation by scanning said converged charged-particle beam in another direction inclined to said one direction, and estimating an astigmatism correction amount from said calculated sharpness value in four directions;
controlling and adjusting said astigmatism of said charged-particle optical system by feeding back said estimated astigmatism correction amount to an astigmatism adjustment means; and
repeating the above operations from converging to controlling until said astigmatism correction amount becomes smaller than a predetermined value. - View Dependent Claims (29, 30, 31, 33, 34)
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32. A method for automatically adjusting astigmatism of a charged-particle beam apparatus, said method comprising:
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converging a charged-particle beam, which is generated by a charged-particle source, by using a charged-particle optical system;
irradiating and scanning in one direction said converged charged-particle beam in an area of a sample, on which a pattern is formed, to obtain an image of said sample by detecting secondary particles generated from said sample by said irradiating and scanning said converged charged-particle beam;
changing a focal position of said converged charged-particle beam;
obtaining a plurality of images of said sample having mutually different focal positions by repeating the operations from converging to changing for plural times;
repeating the operations from converging to obtaining once more by changing said scanning direction of said converged charged-particle bean to be inclined to said one direction at the irradiating and scanning operations, thereby scanning said area on said sample in a direction inclined to that of the previous scanning of said area;
computing an astigmatism of said charged-particle optical system by calculating sharpness values in two directions substantially perpendicular with each other from the plurality of images obtained at said obtaining operation by scanning said converged charged-particle beam in said one direction and sharpness values in another two directions substantially perpendicular with each other from the plurality of images obtained at said obtaining operation by scanning said converged charged-particle beam in another direction inclined to said one direction, and estimating an astigmatism correction amount from said calculated sharpness value in four directions; and
controlling and adjusting said astigmatism of said charged-particle optical system by feeding back said estimated astigmatism correction amount to an astigmatism adjustment means;
optically detecting a height of an object substrate serving as said sample;
controlling a focus of said converged charged-particle beam on the basis of information on said detected height of said object substrate; and
repeating the above operations from converging to controlling until said astigmatism correction amount becomes smaller than a predetermined value.
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Specification