Patent Number: 
Section: claims

1. An electron beam exposure tool, comprising:an electron gun including an electron gun assembly, the electron gun for generating an electron beam; andat least one electron beam splitting lens array, placed in a drift space in said electron gun assembly, adjacent to said electron gun, for splitting the electron beam into a plurality of sub beams to control emittance of said electron beam exposure tool, the drift space being a region that, during operation, is substantially free of electric field lines/gradients originating from outside said drift space. 2. The electron beam exposure tool of claim 1, wherein said at least one lens array is placed in a liner tube, connected to said electron gun assembly. 3. The electron beam exposure tool of claim 2, wherein the liner tube and said electron gun are secured vacuum-tight. 4. The electron beam exposure tool of claim 2, wherein the liner tube and said electron gun are bolted together. 5. The electron beam exposure tool of claim 2, wherein the liner tube and said electron gun are welded together. 6. The electron beam exposure tool of claim 1, said at least one lens array including at least one mesh grid. 7. The electron beam exposure tool of claim 1, said at least one lens array including at least two mesh grids. 8. The electron beam exposure tool of claim 1, said at least one lens array including at least three mesh grids. 9. The electron beam exposure tool of claim 1, said at least one lens array including at least one continuous foil. 10. The electron beam exposure tool of claim 1, said at least one lens array having a transparency between 40-90%. 11. The electron beam exposure tool of claim 1, wherein said electron beans exposure tool is a SCALPEL tool, modified electron beam exposure system (MEBES) tool, or EBES tool. 12. The electron beam exposure tool of claim 1, wherein said lens array increases emittance of an electron beam by producing a divergent beam from an incoming electron beam. 13. The electron beam exposure tool of claim 6, wherein the emittance of the electron beam is increased by a factor substantially equal to (L/d)2, whereL represents a pitch of said at least one mesh grid, andd represents a diameter of a beam crossover created by each opening in said at least one mesh grid. 14. The electron beam exposure tool of claim 8, wherein said at least one lens array includes an odd number of mesh grids, including two outer mesh grids having a curved shape, andwherein spherical aberration of an electron beam passing through said at least one lens array is reduced. 15. A method of controlling beam emittance, comprising:supplying an electron beam with an electron gun including an electron assembly; andsplitting the electron beam via at least one electron beam splitting lens array placed in a drift space in the electron gun assembly, adjacent to the electron gun, the drift space being a region that, during operation, is substantially free of electric field lines/gradients originating from outside said drift space. 16. The method of claim 15, wherein the at least one lens array is placed in a liner tube, connected to said electron gun assembly. 17. The method of claim 16, wherein the liner tube and the electron gun are secured vacuum-tight. 18. The method of claim 16, wherein the liner tube and the electron gun are bolted together. 19. The method of claim 16, wherein the liner tube and the electron gun are welded together. 20. The method of claim 15, wherein the at least one lens array includes at least one mesh grid. 21. The method of claim 15, wherein the at least one lens array includes at least two mesh grids. 22. The method of claim 15, wherein the at least one lens array includes at least three mesh grids. 23. The method of claim 15, said at least one lens array including at least one continuous foil. 24. The method of claim 15, said at least one lens array having a transparency between 40-90%. 25. The method of claim 15, wherein said method is performed by an electron beam exposure tool, including a SCALPEL tool, a modified electron beam exposure system (MEBES) tool, or an EBBS tool.