157 nm: Deepest deep-ultraviolet yet

Lithography at 157 nm is rapidly emerging as the industry-preferred technology for the post-193 nm era. Its target application is for the 100 to 70 nm generations, and it is therefore widely viewed as a “bridge” technology before the next-generation lithographies are ready for insertion into manufacturing. Its attractiveness stems from the overlap in many areas with current practice and shared infrastructure developed for longer wavelengths. This article will review the present status of 157 nm lithography, emphasizing the technological challenges in the various subsystems: lasers, optical materials and coatings, photomask materials, photoresists, and projection tool development. Viewed as a whole, recent developments in these diverse areas are cause for cautious optimism that indeed 157 nm lithography will be ready in time, without encountering unforeseen obstacles.