Charged Particle Inspection Method and Charged Particle System

1 . A charged particle inspection method, comprising:

in a first mode of operation, directing a first number of primary charged particle beamlets onto an object surface, to generate a secondary charged particle beamlet from each of the primary charged particle beamlets incident on the object surface;

directing each of the secondary charged particle beamlets onto a detector arrangement to detect an intensity of each of the secondary charged particle beamlets, wherein a first number of intensities is detected;

in a second mode of operation, directing a second number of the primary charged particle beamlets onto the object surface, wherein the second number is at least one and less than the first number;

directing each of the secondary charged particle beamlets onto the detector arrangement to detect an intensity of each of the secondary charged particle beamlets, wherein a second number of intensities is detected.

2 . The charged particle inspection method according to claim 1 , wherein the first number of primary charged particle beamlets are directed onto the object surface such that an array of beam spots is formed on the surface.

3 . The charged particle inspection method according to claim 2 , further comprising generating image data of the object surface by scanning the array of beam spots across the surface and recording associated intensities of the secondary charged particle beamlets.

4 . The charged particle inspection method according to claim 1 , further comprising obtaining surface charging information by comparing detected intensities of the secondary charged particle beamlets when the first number of primary charged particle beamlets is directed onto the surface with detected intensities of the secondary charged particle beamlets when the second number of primary charged particle beamlets is directed onto the surface.

5 . A charged particle system comprising:

at least one charged particle source;

a first multi aperture plate disposed downstream of the at least one charged particle source, the first multi aperture plate comprising a plurality of apertures;

a second multi aperture plate disposed downstream of the first multi aperture plate, the second multi aperture plate comprising a plurality of apertures;

a controller configured to selectively apply at least first and second voltage differences between the first and second multi aperture plates;

wherein the at least one charged particle source and the first and second multi aperture plates are arranged such that each of a plurality of charged particle beamlets traverses an aperture pair, said aperture pair comprising one aperture of the first multi aperture plate and one aperture of the second multi aperture plate, wherein plural aperture pairs are arranged such that a center of the aperture of the first multi aperture plate is, when seen in a direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced relative to a center of the aperture of the second multi aperture plate.

6 . The charged particle system according to claim 5 , wherein the plural aperture pairs are arranged such that the center of the aperture of the first multi aperture plate is, when seen in the direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced by a distance relative to the center of the aperture of the second multi aperture plate, the distance being less than a diameter of the aperture of the first multi aperture plate.

7 . The charged particle system according to claim 6 , wherein the distance is greater than about 0 . 01 times the diameter of the aperture of the first multi aperture plate.

8 . The charged particle system according to claim 6 , wherein the plural aperture pairs comprise a first group of aperture pairs which are arranged such that the center of the aperture of the first multi aperture plate is, when seen in the direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced by a first distance relative to the center of the aperture of the second multi aperture plate, and wherein the plural aperture pairs comprise a second group of aperture pairs which are arranged such that that the center of the aperture of the first multi aperture plate is, when seen in the direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced by a second distance relative to the center of the aperture of the second multi aperture plate, wherein the second distance is at least 1.05 times the first distance.

9 . The charged particle system according to claim 8 , wherein the plural aperture pairs comprise a third group of aperture pairs which are arranged such that the center of the aperture of the first multi aperture plate is, when seen in the direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced by a third distance relative to the center of the aperture of the second multi aperture plate, wherein the third distance is greater than the first and second distances, and at least 1.10 times the first distance.

10 . The charged particle system according to claim 5 , wherein the apertures of the first multi aperture plate comprised in the plural aperture pairs form a first pattern of apertures, and wherein the apertures of the second multi aperture plate comprised in the plural aperture pairs form a second pattern of apertures which is different from the first pattern.

11 . The charged particle system according to claim 5 , further comprising a beamstop, wherein the first and second multi aperture plates and the beam stop are arranged such that a first number of primary charged particle beamlets bypasses the beam stop when the first voltage difference is applied and further such that a second number of primary charged particle beamlets bypasses the beam stop when the second voltage is applied.

12 . The charged particle system according to claim 11 , wherein the second number is at least one and less than the first number, and wherein a third number of primary charged particle beamlets is incident on the beam stop when the second voltage is applied, wherein the third number is equal to a difference between the first and second numbers.

13 . The charged particle system according to claim 11 , wherein the second number is zero.

14 . The charged particle system according to claim 13 , further comprising a third multi aperture plate disposed upstream of the first multi aperture plate.

15 . The charged particle system according to claim 14 , wherein the third multi aperture plate comprises a plurality of apertures and is arranged such that the aperture pairs each further have an associated aperture of the third multi aperture plate, wherein the associated aperture of the third multi aperture plate is arranged such that a center thereof is, when seen in a direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, substantially aligned with the center of the aperture of the first multi aperture plate of the aperture pair.

16 . The charged particle system according to claim 14 , wherein the controller is further configured to selectively apply at least third and fourth voltage differences between the first and third multi aperture plates.

17 . A charged particle system, comprising:

a source of primary charged particle beamlets;

a field generating arrangement configured to generate at least one of a magnetic or electrical field extending over a space traversed by beam paths of the primary charged particle beamlets,

a beamstop disposed downstream of the field generating arrangement;

a controller configured to selectively switch the field generating arrangement from a first mode of operation to a second mode of operation, wherein a first field associated with the first mode of operation is different from a second field associated with the second mode of operation;

wherein the field generating arrangement and the beamstop are arranged such that a first number of primary charged particle beamlets bypasses the beamstop when the field generating arrangement is switched to the first mode of operation and such that a second number of primary charged particle beamlets bypasses the beamstop when the field generating arrangement is switched to the second mode of operation, wherein the second number is at least one and less than the first number,

and wherein a third number of primary charged particle beamlets is incident on the beamstop when the field generating arrangement is switched to the second mode of operation, wherein the third number is equal to a difference between the first and second numbers.

18 . The charged particle system according to claim 17 , wherein the field generating arrangement comprises

a first pair of electrodes for generating an electrical field between the first pair of electrodes, wherein beam paths of the primary charged particle beamlets traverse a space between the first pair of electrodes;

and wherein the controller is configured to selectively apply a first voltage difference to the first pair of electrodes to generate a first electrical field and a second voltage difference to the first pair of electrodes to generate a second electrical field.

19 . The charged particle system according to claim 18 , wherein an absolute value of the first voltage difference is less than an absolute value of the second voltage difference.

20 . The charged particle system according to claim 18 , wherein an absolute value of the second voltage difference is less than an absolute value of the first voltage difference.

21 . The charged particle system according to claim 17 , wherein, downstream of the beam stop, a beam path of at least one of the primary charged particle beamlets bypassing the beam stop in the first mode of operation coincides with at least one of the primary charged particle beamlets bypassing the beam stop in the second mode of operation.

22 . The charged particle system according to claim 17 , wherein the first pair of electrodes includes two electrode plates which are laterally disposed relative to the beam paths of the primary charged particle beamlets.

23 . The charged particle system according to claim 22 , further comprising at least a second pair of electrodes including two electrode plates which are laterally disposed relative to the beam paths of the primary charged particle beamlets downstream of the first pair of electrodes.

24 . The charged particle system according to claim 18 , wherein the first pair of electrodes includes first and second multi aperture plates having a plurality of apertures formed therein and wherein the apertures plates are oriented transverse to the beam paths of the primary charged particle beamlets, each beam path traversing at least one electrode of the pair of electrodes through one of the apertures formed therein.

25 . The charged particle system according to claim 24 , wherein the first and second multi aperture plates are arranged such that each of a plurality of charged particle beamlets traverses an aperture pair, said aperture pair comprising one aperture of the first multi aperture plate and one aperture of the second multi aperture plate, wherein plural aperture pairs are arranged such that a center of the aperture of the first multi aperture plate is, when seen in a direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced by a distance relative to a center of the aperture of the second multi aperture plate

26 . The charged particle system according to claim 25 , wherein the distance is greater than 0.01 times the diameter of the aperture of the first multi aperture plate.

27 . The charged particle system according to claim 24 , wherein, when seen in a direction of incidence of the charged particle beamlet traversing the one aperture of the first multi aperture plate, a center of each of a fourth number of apertures of the second multi aperture plate is displaced relative to a center of a corresponding one of the apertures of the first electrode by a distance which is less than a diameter of the one aperture of the first electrode, wherein the fourth number is equal to the third number.

28 . The charged particle system according to claim 24 , wherein the beam stop includes at least one multi aperture plate having a plurality of apertures formed therein.

29 . The charged particle system according to claim 17 , wherein the system is configured to direct the beamlets of primary charged particles onto a surface of an object and wherein the system is further configured such that at least the first number of primary charged particle beamlets is directed onto the object surface such that an array of beam spots is formed on the surface.

30 . The charged particle system according to claim 29 , further comprising an objective lens for focusing the primary charged particle beamlets onto the surface of the object.

31 . The charged particle system according to claim 29 , further comprising a detector arrangement for detecting an intensity of secondary charged particles generated by the primary charged particle beamlets having bypassed the beam stop and being incident on the object surface.

32 . The charged particle system according to claim 31 , wherein each primary charged particle beamlet incident on the object surface generates a secondary charged particle beamlet and wherein the detector arrangement is further configured to detect an intensity of each of the secondary charged particle beamlets.

33 . The charged particle system according to claim 32 , wherein the system further comprises a beam splitter for separating the beam paths of the primary charged particle beamlets from beam paths of the secondary charged particle beamlets and for directing the secondary charged particle beamlets onto the detector arrangement.

34 . A particle-optical component for manipulating a plurality of beamlets of charged particles, the particle-optical component comprising:

a first multi aperture plate comprising a plurality of apertures and a second multi aperture plate comprising a plurality of apertures,

the first and second multi aperture plates forming a gap between them,

a controller configured to selectively apply at least a first voltage difference between the first and second multi aperture plates to generate at least a first electrical field between them,

wherein the first and second multi aperture plates are configured and positioned relative to each other such that the first electrical field generated changes a divergence of a set of charged particle beamlets traversing the particle-optical component upon exit from the particle-optical component.

35 . The particle-optical component according to claim 34 , wherein the divergence is changed such that an angle between two charged particle beamlets exiting the particle-optical component is increased or decreased by at least 0.01 mrad.

36 . The particle-optical component according to claim 34 , wherein the divergence is changed such that an angle formed between a peripheral charged particle beamlet having exited the charged particle component and the second multi aperture plate is increased or decreased by at least 0.01 mrad.