Focused charged particle column for operation at different beam energies at a target

摘要

A charged particle column having improved performance at multiple beam energies. The column employs a four-element objective lens to enable improved beam focusing performance at both high and low beam energies at a target, with differing focus voltage configurations for different beam energies. By changing the voltages applied to the four electrodes of the objective lens, different focusing conditions may be rapidly configured, enabling rapid toggling between optimized imaging and optimized processing of a target.

主权项

1. A charged particle column for focusing charged particles over a range of energies from a lowest beam energy to a highest beam energy at a target, comprising:
an optical axis; a charged particle source for generating the charged particles, the source being located on the optical axis; an objective lens for focusing the charged particles onto the target, the objective lens comprising at least a first electrode, a second electrode, a third electrode, and a fourth electrode, the electrodes arranged sequentially along the optical axis, with the first electrode closest to the charged particle source and the fourth electrode closest to the target, and with a first gap between the first and second electrodes, a second gap between the second and third electrodes, and a third gap between the third and fourth electrodes; wherein the first and second gaps are substantially equal and the third gap is no more than ⅓ the size of either the first or second gaps; and wherein the first and fourth electrodes are biased to a first voltage by a first voltage supply, and wherein the objective lens is configured to be switchably operated as a three electrode symmetric lens by switchably biasing the second electrode to a second voltage and the third electrode to the first voltage and as a three electrode asymmetric lens by switchably biasing the second electrode to the first voltage and the third electrode to a third voltage.