Systems and methods of determining aberrations in images obtained by a charged-particle beam tool

A method of determining a setting of a charged-particle beam tool, the method comprising:

• performing an aberration determination method two or more times, each time based on a different estimate for the setting of the charged-particle beam tool, wherein the aberration determination method comprises:
• a) obtaining two or more images of a sample using the charged-particle beam tool, wherein each image is obtained at a known relative difference in a measurement condition of the charged-particle beam tool;
• b) selecting an estimated aberration parameter for the aberrations of a probe profile representing the charged-particle beam used by the charged-particle beam tool;
• c) evaluating an error function indicative of the difference between the two or more images and two or more estimated images that are a function of the estimated aberration parameter and the known relative difference in the measurement condition;
• d) updating the estimated aberration parameter;
• e) performing processes c) and d) iteratively;
• and
• f) determining the final aberration parameter as the estimated aberration parameter that provides the smallest value of the error function;
• determining a residual error for each estimate of the setting by evaluating the error function based on the final aberration parameter determined for the respective estimate of the setting;
• and
• determining as the setting of the charged-particle beam tool the estimate of the setting resulting in the smallest residual error.

A method of determining aberrations in images obtained by a multi-beam charged-particle beam tool, the method comprising:

• performing an aberration determination method for a first beamlet of the multi-beam charged-particle tool, wherein the aberration determination method comprises:
• a) obtaining two or more images of a sample using the charged-particle beam tool, wherein each image is obtained at a known relative difference in a measurement condition of the charged-particle beam tool;
• b) selecting an estimated aberration parameter for the aberrations of a probe profile representing the charged-particle beam used by the charged-particle beam tool;
• c) evaluating an error function indicative of the difference between the two or more images and two or more estimated images that are a function of the estimated aberration parameter and the known relative difference in the measurement condition;
• d) updating the estimated aberration parameter;
• e) performing processes c) and d) iteratively;
• and
• f) determining the final aberration parameter as the estimated aberration parameter that provides the smallest value of the error function,
• wherein the estimated aberration parameter comprises a plurality of estimated aberration values, thereby determining a final aberration parameter comprising a plurality of final aberration values for the first beamlet;
• and
• performing the aberration determination method for each of one or more further beamlets of the multi-beam charged-particle tool,
• wherein, for the aberration determination method for each of one or more further beamlets of the multi-beam charged-particle tool, selecting the estimated aberration parameter comprises selecting one or more final aberration values determined for the first beamlet as corresponding one or more estimated aberration values for each one or more further beamlet, and
• wherein, for the aberration determination method for each of one or more further beamlets of the multi-beam charged-particle tool, updating the estimated aberration parameter comprises updating estimated aberration values that do not correspond to the one or more estimated aberration values that were selected to correspond to the one or more final aberration values determined for the first beamlet.