Study of the effect of layer thickness, beam energy, and metal density on the resistless silicide direct-write electron-beam lithography process for the fabrication of nanostructures

Abstract

To overcome the limitation of resists in electron beam lithography, a resistless electron beam lithography technique was recently developed. In the silicide direct-write electron-beam lithography process (SiDWEL), a thin metallic film is deposited on a silicon surface. A low-energy (<3 keV) electron beam is then used to enable the intermixing of the metal and the silicon layers through thermal effects. A chemical etch is then used to remove the unexposed metal regions. Thermal calculations are performed using a Monte Carlo simulation of electron trajectories and are correlated with experiments using Ni as the thin metallic film. A comparison of the doses required for the formation of several metals is also done. Results show that the SiDWEL process is possible when the electrons lose all their energy in a layer thickness comparable to the phonon mean free path. Finally, experiments are performed using multilayer samples to form silicide structures.