Patent ID: 8242457

Claim:
A charged particle shaped beam column, comprising: a charged particle source; a gun lens configured to provide a charged particle shaped beam approximately parallel to the optic axis of said column; an objective lens configured to form said charged particle shaped beam on the surface of a substrate, wherein the disk of least confusion of said objective lens does not coincide with the surface of said substrate; a first optical element with 8N poles disposed radially symmetrically about the optic axis of said column, said first optical element being positioned between said gun lens and said objective lens, wherein N is an integer greater than or equal to 1 and wherein the 8N poles create a specific desired non-circular beam shape by selectively enlarging aberrations present in said charged particle shaped beam; and a first power supply configured to apply excitations to said 8N poles of said first optical element to provide an octupole electromagnetic field.