High-resolution electron-beam induced deposition

Abstract

A finely focused electron beam is used as a source of energy to decompose molecules, e.g., organometallics or hydrocarbons, adsorbed on the surface of a substrate. Films deposited by these means can be used as etch mask for reactive ion etching, as an absorber for various types of radiation, or directly as part of a device structure. A vector scan electron beam system with a LaB6 cathode has been equipped with a temperature controlled reservoir to supply vapors into a differentially pumped sample chamber. The substrate is mounted on a stage which can be cooled or heated in the range of −40 to +110 °C. The ability to utilize backscattered electron micro- scopy is maintained. Area, line, and spot deposition rates have been measured for tungsten hexacarbonyl [W(CO)6] and dimethyl–gold–trifluoro–acetylacetonate [Me2Au(tfac)] at various fluxes, sample temperatures, and current densities. Three-dimensional buildup of tips and free standing lines across holes in membranes and resolution better than 0.25 μm have been achieved. The composition of the deposited films has been analyzed and each deposit is rich in metal and carbon. Tungsten rich deposits can be used as a highly selective etch mask for oxygen plasmas. Effects limiting the ultimate resolution, such as backscattering from the substrate, and scattering from the deposited material are discussed.