UV and gas interactions in an enclosed 193-nm excimer laser beamline

The implementation of 193nm laser lithography for IC manufacturing is partially dependent on establishing energy efficient laser beam delivery systems of 'beamlines' in wafer steppers and other lithography and metrology tools. The objective of this work is to study the parameters that most critically impact 193nm UV energy efficiency, specifically the elimination of ozone from the beampath by providing an inert gas positive pressure ambient around the laser optics, and the use of 193nm optimized mirrors for beam delivery. An experimental 193nm laser beamline was set up with an ozone monitor and several UV detectors used throughout the optical system. 193nm-optimized laser mirrors were tested in comparison with standard laser mirrors. Three different inert gases were introduced and at various pressures while firing the laser at 50 Hz, 100 Hz, and 200 Hz reprates. Laser pulse energies are reported under these varying conditions as a function of ozone concentration. Overall laser beamline energy transmission is given as a function of laser mirror type.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.