For years, lithographers have applied progressively shorter exposure wavelengths to reduce the minimum feature size on integrated circuit chips. However, this approach recently encountered an unexpected and little-known phenomenon: the intrinsic birefringence of cubic crystals, which could undermine the drive to shorter-wavelength lithography.State-of-the-art large-scale chip fabrication uses 248-nm excimer lasers as illumination sources, and pilot lines are testing prototype 193-nm systems. Next in the progression are 157-nm systems, which have been under intense development for several years. The semiconductor industry has scheduled the introduction of production-level 157-nm steppers within the 2005 to 2007 time frame, with the expectation that these tools will deliver critical feature sizes down to 65 nm…