Lithography with the scanning tunneling microscope

Abstract

In a recent paper [McCord and Pease, J. Vac. Sci. Technol. B 3, 198 (1985)] we described how it should be possible to generate, for lithography and other materials processing, an electron beam with an extraordinary combination of high current (>1 mA), low voltage (<100 V) and small diameter (<0.1 μm) using a modified scanning tunneling microscope (STM) operating in the field emission mode. To test this prediction we have built a modified STM onto the stage of a scanning electron microscope (SEM) so that we can monitor system geometry. The tip, an etched tungsten wire, can be manually moved in the z direction (normal to the target) for coarse motion and three PZT piezoelectric transducers allow 10 μm travel in the x, y, and z directions. A feedback system stabilizes the field emission current (and hence the tip-to-target spacing). We have obtained beams with currents from 1 nA to several microamps at voltages from 1 to 1000 V. We have used the beam to produce lines of contamination on a gold film; the contamination was then used as a mask against sputter etching to produce gold lines. In addition we have exposed a Langmuir–Blodgett resist film. In both cases we have produced sub-tenth-micron lines.