X-ray lithography: the best is yet to come

The competition faced by X-ray lithography from improved optical methods (down to 0.25 mu m) or from a potential breakthrough in fast-electron-beam or ion-beam lithography is examined. The requirements that have to be met for X-ray lithography to become a practical option are discussed. These include a technologically and economically viable source, masks that can withstand the radiation, and lithography machines that provide precise control for circuit pattern overlay at 0.35 mu m and below. The problem of finding a good X-ray resist, once considered a major hurdle, now appears to have become addressable. Current research programs are briefly described.<>