Multi-beam digital scan and image acquisition

A multi-beam charged particle microscope, comprising:

• a first collective raster scanner configured to collectively scan a plurality of primary charged particle beamlets over a plurality of image subfields;
• a detection system comprising a detector configured to detect a plurality of secondary electron beamlets, each secondary electron beamlet corresponding to one of the image subfields;
• and
• a scan control unit connected to the first collective raster scanner to control raster scanning of the plurality of primary charged particle beamlets over the plurality of image subfields;
• and
• an image data acquisition unit connected to the scan control unit and the detector to acquire and select a plurality of image data from the detector in a manner that is synchronized with a clock signal provided by the scan control unit,
• wherein:
• the image data acquisition unit is configured to write the plurality of image data into a parallel access memory at memory locations according to the first selected scan program, and a number of the plurality of image data is at most equal to a number of the plurality of primary charged particle beamlets;
• the scan control unit further comprises:
• a scan generator module connected to the clock unit;
• and
• a first amplifier module connected to the first collective raster scanner;
• the scan generator module is configured to:
• i) generate a sequence of pre-compensation digital scan commands to pre-compensate a scanning induced distortion of the multi-beam charged particle microscope;
• and ii) provide the sequence of pre-compensation digital scan commands to the first amplifier module;
• and
• the first amplifier module is configured to:
• i) generate a first amplified sequence of drive voltages;
• and ii) provide the first amplified sequence of drive voltages to an electrode of the first collective raster scanner.

A multi-beam charged particle microscope, comprising:

• a multi-beam generator configured to generate a plurality of primary charged particle beamlets;
• a first collective raster scanner configured to collectively scan a plurality of primary charged particle beamlets over a plurality of image subfields;
• a second collective raster scanner;
• a detection unit comprising a detector configured to detect a plurality of secondary electron beamlets, each secondary electron beamlet corresponding to one of the image subfields;
• and
• a scan control unit connected to the first collective raster scanner to control raster scanning of the plurality of primary charged particle beamlets over the plurality of image subfields;
• and
• an image acquisition unit connected to the scan control unit and the detector to acquire and select a plurality of image data from the detector in a manner that is synchronized with a clock signal provided by the scan control unit,
• wherein:
• the scan control unit comprises:
• a generic scan generator module comprising a vertex postprocessing unit configured to pre-compensate a scanning induced aberration of the multi-beam charged particle microscope;
• a first amplifier module configured to provide a sequence of high voltages to an electrode of the first collective raster scanner;
• and
• a second amplifier module configured to provide a sequence of high voltages to an electrode of the second collective raster scanner, and
• wherein the image data acquisition unit is configured to write the plurality of image data into a parallel access memory at memory locations according to the first selected scan program, and a number of the plurality of image data is at most equal to a number of the plurality of primary charged particle beamlets.

A multi-beam charged particle microscope, comprising:

• a multi-beam generator configured to generate a plurality of primary charged particle beamlets forming a hexagon;
• a first collective raster scanner configured to collectively scan the plurality of primary charged particle beamlets over a plurality of hexagonal image subfields;
• a second collective raster scanner;
• a detection unit comprising a detector configured to detect a plurality of secondary electron beamlets, each secondary electron beamlet corresponding to one of the hexagonal image subfields;
• a scan control unit connected to the first collective raster scanner to control raster scanning of the plurality of primary charged particle beamlets over the plurality of hexagonal image subfields;
• and
• an image acquisition unit connected to the scan control unit and the detector to acquire and select a plurality of image data from the detector in a manner that is synchronized with a clock signal provided by the scan control unit,
• wherein:
• the image data acquisition unit is configured to write the plurality of image data into a parallel access memory at memory locations according to the first selected scan program, and a number of the plurality of image data is at most equal to a number of the plurality of primary charged particle beamlets;
• the scan control unit further comprises:
• a scan generator module connected to the clock unit;
• and
• a first amplifier module connected to the first collective raster scanner;
• the scan generator module is configured to:
• i) generate a sequence of pre-compensation digital scan commands to pre-compensate a scanning induced distortion of the multi-beam charged particle microscope;
• and ii) provide the sequence of pre-compensation digital scan commands to the first amplifier module;
• and
• the first amplifier module is configured to:
• i) generate a first amplified sequence of drive voltages;
• and ii) provide the first amplified sequence of drive voltages to an electrode of the first collective raster scanner.

A multi-beam charged particle microscope, comprising:

• a multi-beam generator configured to generate a plurality of primary charged particle beamlets;
• a first collective raster scanner configured to collectively scan a plurality of primary charged particle beamlets over a plurality of image subfields;
• a second collective raster scanner;
• a detection unit comprising a detector configured to detect a plurality of secondary electron beamlets, each secondary electron beamlet corresponding to one of the image subfields;
• an objective lens;
• and
• an imaging control module, comprising:
• a scan control unit connected to the first collective raster scanner to control raster scanning of the plurality of primary charged particle beamlets;
• and
• an image acquisition unit connected to the first collective raster scanner to control raster scanning of the plurality of primary charged particle beamlets over the plurality of image subfields, the image acquisition unit configured to control acquisition of an image patch of a surface of a sample with a plurality of scanning lines arranged in a plurality of image subfields,
• wherein:
• the imaging control module is configured to change an orientation of the plurality the scanning lines with respect to an orientation of the sample;
• the image data acquisition unit is configured to write the plurality of image data into a parallel access memory at memory locations according to the first selected scan program, and a number of the plurality of image data is at most equal to a number of the plurality of primary charged particle beamlets;
• the scan control unit further comprises:
• a scan generator module connected to the clock unit;
• and
• a first amplifier module connected to the first collective raster scanner;
• the scan control generator is configured to:
• i) generate a sequence of pre-compensation digital scan commands to pre-compensate a scanning induced distortion of the multi-beam charged particle microscope;
• and ii) provide the sequence of pre-compensation digital scan commands to the first amplifier module;
• the first amplifier module is configured to:
• i) generate a first amplified sequence of drive voltages;
• and ii) provide the first amplified sequence of drive voltages to an electrode of the first collective raster scanner.