Self-referencing health monitoring system for multi-beam SEM tools

1 . A method for monitoring performance of a multi-beam system, the method comprising:

monitoring a performance metric of at least two beams of a plurality of beams of the multi-beam system operating simultaneously during an imaging process, wherein the performance metric of the at least two beams comprises an image parameter or geometric distortion of a first image generated from the imaging process from a field of view (FOV) of a first beam the at least two beams of the plurality of beams and a second image generated from the imaging process of a FOV of a second beam of the at least two beams of the plurality of beams, and wherein the image parameter comprises a noise parameter, an image sharpness parameter, or a resolution parameter;

receiving records of the performance metric of the plurality of beams of the multi-beam system operating during an imaging process, each record associated with a beam of the plurality of beams;

calculating a baseline value of the performance metric of the plurality of beams from a portion of the records;

determining whether an abnormality of the first beam of the at least two beams of the plurality of beams or the second beam of the at least two beams of the plurality of beams occurs based on the calculated baseline value;

providing an abnormality indication in response to the determination that the abnormality has occurred; and

determining, in response to the abnormality indication, whether a source of the abnormality is in the multi-beam system.

2 . A system for monitoring performance of a multi-beam system, the system comprising:

a controller having a circuitry to execute a set of instructions to cause the system to:

monitor a performance metric of at least two beams of a plurality of beams of the multi-beam system operating simultaneously during an imaging process, wherein the performance metric of the at least two beams comprises an image parameter or geometric distortion of a first image generated from the imaging process from a field of view (FOV) of a first beam of the at least two beams of the plurality of beams and a second image generated from the imaging process of a FOV of a second beam of the at least two beams of the plurality of beams, and wherein the image parameter comprises a noise parameter, an image sharpness parameter, or a resolution parameter;

receive records of the performance metric of the plurality of beams of the multi-beam system during the imaging process, each record associated with a beam of the plurality of beams;

calculate a baseline value of the performance metric for the plurality of beams from a portion of the records;

determine whether an abnormality of the first beam of the at least two beams of the plurality of beams or the second beam of the at least two beams of the plurality of beams occurs based on the calculated baseline value;

provide an abnormality indication in response to the determination that the abnormality has occurred; and

determine, in response to the abnormality indication, whether a source of the abnormality is in the multi-beam system.

3 . The system of claim 2 , wherein the set of instructions to cause the system to determine whether the abnormality of the first beam of the at least two beams of the plurality of beams or the second beam of the at least two beams of the plurality of beams occurs further causes the system to:

determine a test value of the first beam or the second beam of the plurality of beams using at least one value of a record of the first beam or the second beam received at multiple time points of the imaging process;

determine whether a difference between the test value of the first beam or the second beam of the plurality of beams and the baseline value is within a predetermined range; and

determine that the abnormality has occurred based on the determination that the difference is not within the predetermined range.

4 . The system of claim 3 , wherein the test value of the first beam or the second beam of the plurality of beams comprises a statistic of the at least one value of the record of the first beam or the second beam of the plurality of beams.

5 . The system of claim 2 , further comprising:

a database configured to store at least one of the baseline value or the records.

6 . The system of claim 5 , wherein the set of instructions further cause the system to:

retrieve at least one of the records or the baseline value from the database before determining whether the difference is within the predetermined range.

7 . The system of claim 2 , wherein the set of instructions further cause the system to:

calculate the baseline value after a predetermined event.

8 . The system of claim 7 , wherein the set of instructions to cause the system to calculate the baseline value after the predetermined event further causes the system to:

calculate the baseline value based on initial records of the performance metric received after the predetermined event.

9 . The system of claim 7 , wherein the predetermined event comprises completion of one of maintenance of the multi-beam system or calibration of the multi-beam system.

10 . The system of claim 7 , wherein the predetermined event comprises that each value of the records changes by a shift value, wherein the shift value does not deviate from an average value of the values of the records exceeding a predetermined range.

11 . The system of claim 2 , wherein the set of instructions further cause the system to:

calculate the baseline value as a statistic of values of the portion of the records.

12 . The system of claim 11 , wherein the statistic comprises one of a mean value, a median value, a variance value, a standard deviation value, or a root mean square value.

13 . The system of claim 3 , wherein the test value of the first beam or the second beam of the plurality of beams comprises a value of the record of the first beam or the second beam received at one of the multiple time points.

14 . The system of claim 2 , wherein the set of instructions to cause the system to determine whether the abnormality of the first beam of the plurality of beams or the second beam of the at least two beams of the plurality of beams occurs further causes the system to:

determine a first regression parameter from a regression performed on values of the record received at multiple time points, and second regression parameters from regressions performed on values of each of the portion of the records received at the multiple time points, each of the second regression parameters corresponding to one of the portion of the records;

determine the baseline value using the second regression parameters;

determine whether a difference between the first regression parameter and the baseline value is within a predetermined range; and

determine the abnormality occurs based on a determination that the difference is not within the predetermined range.

15 . A non-transitory computer-readable medium that stores a set of instructions that is executable by at least one processor of an apparatus to cause the apparatus to perform a method for monitoring performance of a multi-beam system, the method comprising:

monitoring a performance metric of at least two beams of a plurality of beams of the multi-beam system operating simultaneously during an imaging process, wherein the performance metric of the at least two beams comprises an image parameter or geometric distortion of a first image generated from the imaging process from a field of view (FOV) of a first beam of the at least two beams of the plurality of beams and a second image generated from the imaging process of a FOV of a second beam of the at least two beams of the plurality of beams, and wherein the image parameter comprises a noise parameter, an image sharpness parameter, or a resolution parameter;

receiving records of the performance metric of the plurality of beams of the multi-beam system during the imaging process, each record associated with a beam of the plurality of beams;

calculating a baseline value of the performance metric of the plurality of beams from a portion of the records;

determining whether an abnormality of the first beam of the at least two beams of the plurality of beams or the second beam of the at least two beams of the plurality of beams occurs based on the calculated baseline value;

providing an abnormality indication in response to the determination that the abnormality has occurred; and

determining, in response to the abnormality indication, whether a source of the abnormality is in the multi-beam system.