Sub-0.1-um NMOS transistors fabricated using point-source x-ray lithography

As transistor features shrink into the deep submicron range, a corresponding reduction in the optical wavelength used to pattern such features has also continued. Currently, advanced optical steppers found in ULSI production applications operate at a wavelength of 365 nm with 248 nm optical lithography present in process development facilities and 193 nm lithography in the early stages of research. By reducing the wavelength still further to below 1.5 nm, x-ray lithography represents the ultimate limit of this paradigm. In this paper we present the experimental results of the first MOSFETs ever fabricated using a laser plasma-source x-ray stepper. These transistors were patterned using a mix-and-match lithography scheme where the gate level was printed using a 1.4 nm plasma-source x-ray stepper while the other layers were patterned using an optical stepper operating at a wavelength of 248 nm (DUV). The minimum gate length of these transistors is 0.12 μm with an effective channel length of 75 nm.