Optical Microlithography

Abstract

"Projecting the course of future development in lithography is perilous, however, because we are approaching serious limitations in both device design and optical lithography." Four years ago Phillip IBlais gave this warning in his guest editorial for the special issue of Optical Engineering dedicated to Submicron Lithography. That special issue had no papers on optical tooling but reported on electron-beam, x-ray, and ion-beam lithographies, with obvious implications for the future of optical lithography. Since then, the numerical apertures of lenses have in creased, the exposing wavelengths have shortened, and one-half micrometer optical lithography has been demonstrated. With the aid of new resists, excimer lasers, and exotic deep-UV optics, production of integrated circuits with even smaller critical dimensions is being seriously considered. Optical lithography is entering an exciting new era, driven by optical engineers pushing the evolution of this technology into realms previously assumed to be beyond its limits. With operating bandwidths greater than 1 x 109 pixels/s and rapidly rising, optical lithography tooling is continuing to be the workhorse for patterning wafers, even as the critical dimensions continue to decrease. The authors of this special issue were invited to show us how this is happening.