Method and system for the removal and/or avoidance of contamination in charged particle beam systems

1. A charged particle beam system, comprising:

a beam generator module for generating a beam of charged particles;

a charged particle optical column comprising a charged particle optical element for projecting the beam of charged particles onto a target;

a source for providing cleaning agent;

a conduit connected to the source and arranged for introducing the cleaning agent towards the charged particle optical element; and

a restriction element provided between the beam generator module and the charged particle optical column to at least reduce a flow of the cleaning agent into the beam generator module,

wherein the source is configured to introduce the cleaning agent during operation of the beam generator module, and wherein the beam generator and the charged particle optical column are positioned in a common vacuum chamber during the operation of the beam generator module.

2. The charged particle beam system of claim 1 , wherein the restriction element is movably connected to the beam generator module and configured to abut the charged particle optical column.

3. The charged particle beam system of claim 2 , wherein the restriction element is connected to a first wall of the beam generator module, the restriction element at least partly surrounding a perimeter of an opening in the first wall for passage of the beam of charged particles, wherein the restriction element comprises an at least partially ring-shaped element, the at least partially ring-shaped element being movably arranged with respect to the first wall in a direction toward or away from the charged particle optical column.

4. The charged particle beam system of claim 3 , further comprising a confining element for confining a movement of the restriction element with respect to the first wall.

5. The charged particle beam system of claim 4 , wherein the restriction element is provided with one or more protrusions and the confining element is arranged to cooperate with the protrusions to confine movement of the restriction element.

6. The charged particle beam system of claim 1 , wherein the charged particle optical element comprises:

a charged particle transmitting aperture for transmitting and/or influencing the beam of charged particles, and

a vent hole for providing a flow path between a first side and a second side of the charged particle optical element,

wherein the vent hole has a larger cross section than a cross section of the charged particle transmitting aperture.

7. The charged particle beam system of claim 6 , wherein the vent hole has a cross section of one of the following shapes: circular, slit-shaped, or elliptical.

8. The charged particle beam system of claim 6 , wherein the charged particle optical element comprises a plurality of the vent holes and a plurality of the charged particle transmitting apertures, the vent holes arranged next to the charged particle transmitting apertures.

9. The charged particle beam system of claim 8 , wherein the charged particle transmitting apertures are arranged in one or more groups and the vent holes are arranged substantially along the one or more groups.

10. The charged particle beam system of claim 9 , wherein the vent holes are arranged in one or more one dimensional arrays.

11. The charged particle beam system of claim 9 , wherein the vent holes are arranged in one or more two-dimensional arrays.

12. The charged particle beam system of claim 9 , wherein the vent holes are arranged on either sides of the one or more groups of plurality of charged particle transmitting apertures.

13. The charged particle beam system of claim 8 , wherein the vent holes are arranged immediately adjacent an area comprising a plurality of the charged particle transmitting apertures.

14. The charged particle beam system of claim 8 , wherein the vent holes are arranged with a pitch which is equal to or larger than a dimension of the vent holes, the pitch being in the range from 1 to 3 times the dimension of the vent holes.

15. The charged particle beam system of claim 14 , wherein the pitch is equal to or larger than a dimension of the vent holes along a direction of alignment of the vent holes.

16. The charged particle beam system of claim 6 , wherein the system is configured such that a charged particle passing through the vent hole is prevented from reaching the target.

17. The charged particle beam system of claim 1 , wherein the beam generator module is maintained in an operable vacuum range of the beam generator module while the cleaning agent is introduced.

18. The charged particle beam system of claim 1 , wherein the restriction element is configured to restrict a flow path between the beam generator module and the charged particle optical column such that the cleaning agent is introduced during operation of the beam generator module.

19. The charged particle beam system of claim 2 , wherein the restriction element abuts the charged particle optical column by means of gravity and/or a spring force.

20. The charged particle beam system of claim 1 , wherein the common vacuum chamber is maintained in an operable vacuum range of the beam generator module while the cleaning agent is introduced.