The increasing use of Argon Fluoride (ArF) 193 nm excimer lasers in microlithography, surgical procedures and other applications have created the requirement for an increasingly larger number of specialized optical components and thin film coatings. At 193nm these include coated components that can withstand long duration exposure to UV radiation without significant change in performance. Similar coatings and components for Fluorine lasers operating at 157 nm are under development. At these deep UV wavelengths, potential coating materials as well as substrates are very limited due to absorption and impurities. Characteristics of various types of thin film coatings including reflective, anti-reflective, beam-splitting, beam attenuating and optical bandpass filters, at both 193nm and 157nm, are measured using a specially designed vacuum spectrophotometer system. Results of these measurements as well as plans for further coating development are presented.
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.