Advanced lithography for ULSI

Lens technology has advanced to the point where lithographic feature sizes equal to, or even smaller than, the wavelength of the light used in the stepper can be achieved in production. How far optical lithography can go from here depends both on how short a wavelength is possible and how close we can come to the absolute limit of diffraction. In this article, we will examine the current thinking on these questions, and discuss what might happen if and when optical lithography really can no longer be used.