Novel lithography and signal processing with water vapor ions

A novel model is presented for the operation of field emission sources in air. Under this condition the cathode-anode distance is less than the mean free path for the particles emitted in air. Such conditions are encountered in scanning tunneling microscope lithography in air and in novel integrated microtriode tube devices designed to operate in air. In air, the presence of a high electric field gradient, produced at the tip, will cause the polar water molecules coating the surface to align with the field and move to the high field region. As a result, a Taylor cone of water, like that as it is observed with liquid metal ion sources, will form. The high electric field gradient at the Taylor cone, enhanced by the high dielectric constant, will produce a very finely focused beam of ions. We examine the case of water ion formation. With a positive tip bias, hydronium ions will form at electric fields of 1 V/nm. This is a factor of 4 smaller than that required to produce the field emission with electrons. The electric field distribution and the hydronium ion trajectories from a metal tip with a high permittivity material cone are calculated. The spot size of the ion beam on the substrate was 2.9 nm. A model for lithography, based on water ions, is presented. The model is applied to the design of a microtriode device for signal processing. The three-dimensional fabrication of such a device by e-beam induced chemical vapor deposition is demonstrated. (C) 1997 American Vacuum Society. [S0734-211X(97)03804-3].