Publications

High rate gas dosing for tip based nanofabrication processes

Kanouff, Michael P.; Randall, J.N.; Nadesalingham, M.; Kirk, W.P.; Wallace, R.M.

Tip based nanofabrication (TBN) processes promise unprecedented degrees of control and precision for the manufacture of nanostructured materials and devices. These processes use atomic force microscope or scanning tunneling microscope tips to create localized electric fields, electron beams, and other catalyzing conditions to control and detect the position, size, dimension, and orientation of nanostructures. Tip based approaches have deposited metals, oxides, and organic molecules to name a few. Often, a gas phase precursor is required to provide the material for the deposit. The TBN conditions for gas dosing are unique compared to other fabrication processes, e.g., chemical vapor deposition. The manufacture of precision nanostructures requires a contamination-free environment, and hence ultrahigh vacuum conditions must be maintained in the chamber. This can cause a gas jet from a doser to spread into a wide fan resulting in a small precursor flux with a broad distribution. This makes it difficult to meet the large fabrication rates desired for TBN. Ideally, gas dosing would promote rapid deposition rates while limiting the chamber pressure by creating a focused gas jet that is restricted to the intended fabrication area. Continuum gas dynamics and direct simulation Monte Carlo calculations were used to study the effect of design and operational parameters on gas doser performance. The source pressure, doser design, and operating conditions are shown to affect the flux distribution at the substrate. The calculated results are compared to experimental measurements. A novel gas doser design was identified and its performance predicted. © 2009 American Vacuum Society.