Sectored magnetic lens and method of use

A method for applying a magnetic field to a charged particle beam, comprising:

• directing the charged particle beam through a magnetic lens from a first end of the magnetic lens to a second end of the magnetic lens, the magnetic lens comprising:
• an outer pole piece and an inner pole piece, wherein the outer pole piece is magnetically coupled to the inner pole piece, wherein the outer pole piece comprises at least two sectors and at least two slots, and wherein each sector is disposed between lateral boundaries of the two slots in the outer pole piece;
• a primary coil winding interposed between the outer pole piece and the inner pole piece, wherein the primary coil winding is configured to drive a magnetic potential of the outer pole piece relative to the inner pole piece during use;
• and
• at least two sector coil windings, wherein each sector coil winding is coupled to one sector of the outer pole piece, wherein each sector coil winding is configured to drive a magnetic potential of one sector of the outer pole piece during use, and wherein the magnetic field applied to the charged particle beam comprises the magnetic potential of the outer pole piece and the magnetic potentials of at least one sector of the outer pole piece;
• applying a first current to the primary coil winding of the magnetic lens;
• and
• applying a second current to at least one of the two sector coil windings.

A system configured to inspect a specimen during use, comprising:

• a charged particle beam source configured to generate a charged particle beam during use;
• a magnetic lens configured to apply a magnetic field to the charged particle beam during use, wherein the magnetic lens is configured along a path of the charged particle beam, the magnetic lens comprising;
• an outer pole piece and an inner pole piece, wherein the outer pole piece is magnetically coupled to the inner pole piece, wherein the outer pole piece comprises at least two sectors and at least two slots, wherein each sector is disposed between lateral boundaries of the two slots of the outer pole piece, and wherein the charged particle beam is configured to pass through the magnetic lens from a first end of the magnetic lens to a second end of the magnetic lens during use;
• a primary coil winding interposed between the outer pole piece and the inner pole piece, wherein the primary coil winding is configured to drive a magnetic potential of the outer pole piece relative to the inner pole piece during use;
• and
• at least two sector coil windings, wherein each sector coil winding is coupled to one sector of the outer pole piece, wherein each sector coil winding is configured to drive a magnetic potential of one sector of the outer pole piece during use, and wherein the magnetic field applied to the charged particle beam comprises the magnetic potential of the outer pole piece and the magnetic potential of at least one sector of the outer pole piece;
• and
• a stage configured to support at least a portion of the specimen during use, and wherein the stage is positioned along the path of the charged particle beam.