Optical lithography stalls X-rays

The revival in optical lithography resulting from continuing advances in photoresists, phase-shifting masks, high-numerical-aperture step-and-repeat optical systems, multilevel-resist processing, and top-surface imaging techniques is discussed. Optical lithography is being used to make advanced IC chips, with 0.35 mu m geometries in research, 0.5 mu m in production. Ultraviolet (UV) light in the 200-400 nm range is the predominant system for IC manufacturing technology. Deep-UV lithography is not yet accepted for production processes, mostly due to the lack of commercially available positive and negative-tone photoresist systems for deep-UV wavelengths. In addition, negative-tone resists are temperature-sensitive and therefore hard to handle in a manufacturing environment, extensive gas-handling facilities are required for deep-UV excimer laser sources, and optical components have to be replaced often because the intense laser energy devitrifies lenses quickly.<>