Advanced lithography for nanofabrication

A novel method for generating lateral features by patterning the naturally forming surface hydride layer on Si is described. Because of the relatively strong chemical bonding between silicon and hydrogen, the hydride layer acts as a robust passivation layer with essentially zero surface mobility at ordinary temperatures. A focused electron beam from a scanning electron microscope was used for patterning. Upon losing the hydrogen passivation the silicon surface sites become highly reactive. Ideally, the lifetime of such a pattern in a clean environment should be infinite. Deliberate exposure of the entire wafer to a suitable gas phase precursor results in selective area film growth on the depassivated pattern. Linewidths and feature sizes of silicon dioxide on silicon below 100 nm were achieved upon exposure to air. The silicon dioxide is robust and allows effective pattern transfer by anisotropic wet-chemical etching. In this paper, the mechanism of hydrogen desorption and subsequent pattern formation, and the factors that govern the ultimate pattern resolution will be discussed.