Lithography laser system with in-place alignment tool

Abstract

The present invention provides a modular high repetition rate ultraviolet gas discharge laser light source for a production line machine. The system includes an enclosed and purged beam path with optical components adjustable from outside of the enclosure without the need to open it. Targets and beam directors are included within the beam path enclosure and are used to judge the quality of alignment. These target and beam directors are located on a moveable mount which is insertable in the beam path for alignment and are removed out of the beam path for normal operation. The positions of the targets and beam directors are controlled from outside the beam path enclosure. In preferred embodiments, the production line machine is a lithography machine and two separate discharge chambers are provided, one of which is a part of a master oscillator producing a very narrow band seed beam which is amplified in the second discharge chamber. This MOPA system is capable of output pulse energies approximately double the comparable single chamber laser system with greatly improved beam quality. A pulse stretcher more than doubles the output pulse length resulting in a reduction in pulse power (mJ/ns) as compared to prior art laser systems. In a preferred embodiment the beam directors clients laser beam being aligned to a monitor outside the beam path enclosure to permit the normal to image a cross-section of the beam and the target.