Evaluation of molybdenum silicide for use as a 193 nm phase-shifting absorber in photomask manufacturing

The introduction of 193-nm lithography is expected to provide a one-generation improvement in lithographic imaging capability. This will only happen if all of the enhancements presently being used for 248-nm lithography are also available at 193 nm. Attenuating phase shift materials have been developed by a few mask vendors for use at 193 nm. A molybdenum silicide phase shifting absorber has been developed by Hoya and evaluated by IBM and Hoya. Transmission and phase uniformity have been evaluated, and the contribution to these values from film thickness and etch variations have been identified. Plate-to-plate uniformity of phase and transmission have been measured. Durability of the film has been tested against 193-nm radiation exposure and chemical cleaning methods. Defect levels have been measured in the unprocessed film and the finished mask. The inspectability of masks made with this material has been evaluated on commercial inspection systems. The 193-nm molybdenum silicide film is compatible with etch and repair processes developed for 248-nm molybdenum silicide mask absorbers. The 193-nm molybdenum silicide film has a transmission of 6%, which is suitable for most attenuating phase shift applications. The film may be extendable to higher transmission values.