Damage-limited lifetime of 193-nm lithography tools as a function of system variables

Model diffraction-limited optical systems are examined for the effects of radiation-induced compaction on optical performance. The Zernike phase aberration terms resulting from 193-nm-induced compaction in a model lithographic system are calculated with Fourier optics and ray tracing. Using experimental densification rates and the extracted aberration terms, we develop equations describing a useful system lifetime as a function of relevant system variables. In the example examined, the useful life depends strongly on the throughput, resist sensitivity, and partial coherence.