Alignment determination method and computer program

1 . A method of determining alignment of electron optical components operable on a plurality of beamlets in a charged particle apparatus comprising: an aperture array and a detector configured to detect charged particles corresponding to the beamlets that pass through the corresponding apertures in the aperture array, the detector positioned downbeam along the paths of the beamlets relative to the aperture array, the method comprising:

scanning each beamlet in a plane of the aperture array over a portion of the aperture array in which a corresponding aperture of the aperture array is defined so that charged particles of each beamlet may pass through the corresponding aperture;

detecting during the scan any charged particles corresponding to each beamlet that passes through the corresponding aperture;

generating a detection pixel for each beamlet based on the detection of charged particles corresponding to each beamlet at intervals of the scan;

collecting information comprised in the detection pixel such as the intensity of charged particles;

generating, for each beamlet, an image representative of the intensity of detected signal particles corresponding to the scan of the beamlet over the portion of the aperture array in which its corresponding aperture is defined; and

determining a parameter set of at least one beamlet relating to dimensions of the at least one beamlet in a plane of the aperture array, based on the image corresponding to the at least one beamlet.

2 . The method of claim 1 , wherein the detecting comprises detecting any charged particles corresponding to each beamlet that pass through the corresponding aperture at the intervals during the scan.

3 . The method of claim 1 , further comprising generating, based on a plurality of the images for the plurality of beamlets, a combined image, representative of the scan of the plurality of beamlets over the aperture array.

4 . The method of claim 3 , wherein the combined image comprises the collected information of each interval for the plurality of beamlets.

5 . The method of claim 3 , wherein the positions of the images represented in the combined image are determined based on the physical positions of the corresponding apertures in the aperture array.

6 . The method of claim 3 , wherein the distances between the images represented in the combined image are determined based on the relative positions of the corresponding apertures in the aperture array.

7 . The method of claim 1 , wherein the parameter set comprises a shape of the at least one beamlet in the plane of the aperture array and/or one or more dimensions of the at least one beamlet in the plane of the aperture array.

8 . The method of claim 1 , wherein the parameter set comprises a characteristic of information of the detection pixels, for example a variation in the characteristic of the detection pixels, such as the variation in intensity of the detection pixels.

9 . The method of claim 1 , wherein the parameter set relates to a plurality of beamlets.

10 . The method of claim 9 , wherein the determining the parameter set comprises determining a plurality of individual beam parameter sets each relating to a single beamlet and generating the parameter set from the plurality of individual beam parameter sets or determining the parameter set from a combined image comprising detection pixels relating to multiple beamlets.

11 . The method of claim 9 , wherein the parameter set comprises an alignment parameter set of the plurality of beamlets in the plane of the aperture array.

12 . The method of claim 11 , wherein the alignment parameter set comprises the relative intensity, position and/or shape of the beamlets represented in the parameter set.

13 . The method of claim 1 , wherein the charged particle apparatus has a set of settings, the method further comprising changing at least one setting of the set of settings based on the parameter set.

14 . The method of claim 1 , wherein the scanning comprises scanning each beamlet along a scanning path having a main scanning direction and a sub-scanning direction, the main scanning direction being different from the sub-scanning direction.

15 . The method of claim 14 , wherein the plurality of beamlets having a beam pitch in the plane of the aperture array, wherein the distance each beamlet is scanned over the corresponding portion of the aperture array in the main scanning direction is less than a number of beam pitches.

16 . The method of claim 1 , wherein the electron optical components of the charged particle apparatus further comprising an additional aperture array disposed along and upbeam the paths of the beamlets relative to the aperture array, the method further comprising:

directing the plurality of beamlets through the additional aperture array disposed upbeam of the aperture array towards the aperture array,

wherein the scanning comprises directing the beamlets through the corresponding apertures in the aperture array.

17 . A non-transitory computer readable medium that stores a set of instructions for determining alignment of electron optical components operable on a plurality of beamlets in a charged particle apparatus comprising: an aperture array and a detector configured to detect charged particles corresponding to the beamlets that pass through the corresponding apertures in the aperture array, the detector positioned downbeam along the paths of the beamlets relative to the aperture array, the set of instructions configured to cause one or more processors of the charged particle apparatus to perform operations comprising:

control the charged particle apparatus to scan each beamlet in a plane of the aperture array over a portion of the aperture array in which a corresponding aperture of the aperture array is defined so that charged particles of each beamlet may pass through the corresponding aperture;

control the charged particle apparatus to detect during the scan any charged particles corresponding to each beamlet that passes through the corresponding aperture;

generate a detection pixel for each beamlet based on the detection of charged particles corresponding to each beamlet at intervals of the scan;

collect information comprised in the detection pixel such as the intensity of charged particles;

generating, for each beamlet, an image representative of the intensity of detected signal particles corresponding to the scan of the beamlet over the portion of the aperture array in which its corresponding aperture is defined; and

determining a parameter set of at least one beamlet relating to dimensions of the at least one beamlet in a plane of the aperture array, based on the image corresponding to the at least one beamlet.