Image-formation apparatus using charged particle beams under various focus conditions

An image-formation apparatus using charged particle beams comprising:

• a charged particle source for emitting charged particle beams under various focus conditions changed in a stepwise manner;
• a scan deflector for scanning a charged particle beam emitted from the charged particle source on a sample;
• a charged particle detector for detecting charged particles emitted from a plurality of points on a surface portion of said sample in response to the charged particle beams under various focus conditions, and for generating a pixel signal corresponding to each of the various focus conditions for each of the plurality of points in response to the detected charged particles;
• and
• a storage medium for storing pixel signals output from the charged particle detector;
• and
• a data processing system configured to perform the machine-implemented steps of:
• reading signals from the storage medium,
• determining an in-focus status of the pixel signal corresponding to each of the various focus conditions for each of the plurality of points;
• for each of the plurality of points on said surface portion of said sample, selecting a preferred pixel signal from pixel signals corresponding to each of the various focus conditions for each of the plurality of points based on in-focus statuses thereof;
• and
• generating an image of said surface portion of said sample based on the preferred pixel signals corresponding to the plurality of points on said surface portion of said sample.

An image-formation apparatus using charged particle beams comprising:

• a charged particle source for emitting charged particle beams under various focus conditions changed in a stepwise manner;
• a scan deflector for scanning a charged particle beam emitted from the charged particle source on a sample;
• a charged particle detector for detecting charged particles emitted from a plurality of points on a surface portion of said sample in response to the charged particle beams under various focus conditions, and for generating a pixel signal corresponding to each of the various focus conditions for each of the plurality of points in response to the detected charged particles;
• a plurality of frame memories, each of which is configured to store pixel signals for the plurality of points corresponding to one of the various focus conditions, wherein each of said plurality of frame memories has memory units for storing the pixel signal corresponding to each of the plurality of points corresponding to one of the various focus conditions;
• and
• a data processing system configured to perform the machine-implemented steps of:
• determining in-focus statuses of the pixel signals stored in the plurality of frame memories;
• for each of the plurality of points on said surface portion of said sample, selecting a preferred pixel signal from pixel signals corresponding to each of the various focus conditions for each of the plurality of points based on in-focus statuses thereof;
• and
• storing the preferred pixel signal for each of the plurality of points to corresponding memory unit of one of the plurality of frame memories.

An image-formation apparatus using charged particle beams having means for adjusting a focus condition of a charged particle beam and constructing an image of a sample using irradiation of said charged particle beam, comprising:

• a storage medium for storing a sample image obtained for each of various focus conditions;
• and
• a data processing system configured to perform the machine-implemented steps of:
• reading sample images corresponding to each of the various focus conditions from the storage medium;
• determining an in-focus status of each of a plurality of points on the sample images corresponding to each of the various focus conditions;
• for each of the plurality of points, selecting a preferred pixel from the sample images corresponding to the various focus conditions based on in-focus statuses thereof;
• and
• generating an image of said sample based on the preferred pixel for each of the plurality of points.

An image-formation apparatus using charged particle beams comprising:

• a charged particle source for emitting charged particle beams under various focus conditions;
• a scan deflector for scanning a charged particle beam emitted from the charged particle source on a sample;
• a charged particle detector for detecting charged particles emitted from a plurality of points on a surface portion of said sample in response to the charged particle beams under various focus conditions, and for generating a pixel signal corresponding to each of the various focus conditions for each of the plurality of points in response to the detected charged particles;
• a storage medium for storing pixel signals output from the charged particle detector for each of the various focus conditions;
• and
• a data processing system configured to perform the machine-implemented steps of:
• reading pixel signals from the storage medium;
• determining an in-focus status of the pixel signal corresponding to each of the various focus conditions for each of the plurality of points;
• for each of the plurality of points on said surface portion of said sample, selecting a preferred pixel signal from pixel signals corresponding to each of the various focus conditions for each of the plurality of points based on in-focus statuses thereof;
• and
• generating an image of said surface portion of said sample based on the preferred pixel signals corresponding to the plurality of points on said surface portion of said sample;
• wherein said generating step is performed in parallel with changing the focus conditions of the charged particle beam.

An image-formation apparatus using charged particle beams having means for adjusting a focus of a charged particle beam and constructing an image of a sample based on scanning of said charged particle beam on the sample, comprising:

• a storage medium for storing a sample image obtained for each adjusted focus;
• selecting means for selecting a specific area of a sample image stored in the storage medium;
• and
• means for replacing the sample image whose area has been selected by the selecting means, with a sample image having a different focus or another image.

An image-formation apparatus using charged particle beams comprising:

• a charged particle source;
• a lens for converging and irradiating a charged particle beam emitted from the charged particle source onto a sample;
• a detector for detecting secondary charged particles obtained at a portion irradiated with said charged particle beam;
• a display device for displaying a sample image based on charged particles obtained by the detector;
• means for storing position information in an irradiation direction of the charged particle beam for each specific position in the sample image displayed in the display device;
• a specifying means for specifying an arbitrary position in a display screen of the display device;
• and
• means for calculating a distance between two positions specified by said specifying means in said irradiation direction of the charged particle beam, based on position information about at least the two positions.

An image-formation apparatus using charged particle beams comprising:

• means for adjusting a focus of a charged particle beam;
• means for constructing a sample image based on scanning of said charged particle beam on the sample;
• means for measuring dimensions of an observation target on the sample based on the sample image;
• a storage medium for storing a plurality of sample images obtained for each adjusted focus;
• and
• image forming means for selecting a specific sample image from said plurality of sample images, and forming another sample image using pixels from the specific sample image having a focus evaluation value more than a predetermined value;
• wherein said image-formation apparatus performs said measuring of dimensions based on the another sample image formed by the image forming means.

A beam scanning inspection apparatus for forming a sample image based on signals obtained by scanning a beam on the sample, said beam scanning inspection apparatus comprising:

• focus changing means for changing a focus of said beam in a stepwise manner;
• a storage medium for storing a sample image for each focus changed by the focus changing means;
• means for overlapping sample images stored in the storage means to form another sample image;
• means for forming a line profile based on the overlapped sample image;
• and
• means for measuring dimensions based on the line profile.

An electron beam apparatus for obtaining a scan image of a sample, comprising beam converging means for thinly converging a primary electron beam emitted from an electron source using an object lens, beam scanning means for scanning primary electrons on a sample, detecting means for detecting secondary signals generated from the sample by scanning the beam on the sample, and image forming means for forming a sample image using the secondary signals, said apparatus comprising:

• focus control amount determination means for determining an amount of change in a beam convergence position;
• focus control means for controlling beam focal conditions according to the focus control amount;
• image quantity determination means for determining the number of images;
• image capturing means for capturing a plurality of images of the sample each under a different focal condition controlled by the focus control means, wherein the each of the images have pixels corresponding to a plurality of points on the sample;
• storage means for storing the plurality of images;
• and
• a data processing system configured to carry out the machine-implemented steps of:
• accessing the plurality of images from the storage means;
• determining in-focus statuses for the pixels on each of the plurality of images under different focal conditions;
• for each of the plurality of points, selecting a preferred pixel from the pixels corresponding to the same point of the plurality of points based on the in-focus statuses thereof;
• and
• generating an image of the sample using the preferred pixel for each of the plurality of points.

An electron beam apparatus for obtaining a scan image of a sample, comprising beam converging means for thinly converging a primary electron beam emitted from an electron source using an object lens, beam scanning means for scanning primary electrons on a sample, detecting means for detecting secondary signals generated from the sample by scanning the beam on the sample, and image forming means for forming a sample image using the secondary signals, said apparatus comprising:

• focus control amount determination means for determining a beam convergence position change amount;
• focus control means for controlling beam focal conditions according to the focus control amount;
• image quantity determination means for determining the number of images;
• image capturing means for capturing a plurality of images of the sample each under a different focal condition controlled by the focus control means, wherein the each of the images have pixels corresponding to a plurality of points on the sample;
• storage means for storing the plurality of images;
• image constructing means for constructing an image of the sample using the plurality of stored images, wherein the image constructing means is configured to carry out the machine-implemented steps of:
• accessing the plurality of images from the storage means;
• determining in-focus statuses for the pixels on each of the plurality of images under different focal conditions;
• for each of the plurality of points, selecting a preferred pixel from the pixels corresponding to the same point of the plurality of points based on the in-focus statuses thereof;
• and
• generating an image of the sample using the preferred pixel for each of the plurality of points.