Fast Curvature Actuator for High-Power Laser Beam Size and Focus Control

摘要

In a beam transport system of a lithographic apparatus, for example an extreme ultraviolet (CUV) lithographic apparatus, a laser beam may he actuated by mirrors to control the laser beam size, divergence and focus. A known technique of actuating a laser beam in an EUV lithographic apparatus is the use of curved mirrors. To achieve the desired actuation, a mirror may be chosen from a plurality of mirrors with predefined curvature in dependence on the laser divergence and beam trans port system length. However, the discrete set of curvatures available does not allow for correction of transients (e.g. in the start-up or shut-down of the laser beam), and also results in a reduction of performance and power as well as downtime of the EUV lithographic apparatus due to the swapping out of the mirrors.