PLASMA CHARGING AT THE NANOMETER SCALE:

Precise determination of the rate and asymmetry of surface charging has been an issue of great importance in a range of scientific and technological areas. In particular, differential charging is often a serious drawback in applying plasma processing technology to define high aspect ratio structures in the manufacturing of modern microelectronic and photonic devices and micro- and nanoelectrochemical systems. Moreover charging-induced discharges can significantly affect product yields. It is well established that charges can accumulate on the exposed insulating surfaces of patterned structures during plasma exposure, due to the directionality differences between impinging ions and electrons. This, in turn, gives rise to electric fields which can alter the trajectory, flux, and kinetic energy of incident ions, often resulting in undesirable side effects in the plasma-assisted processes. Earlier theoretical studies have focused on describing the mean behavior of surface charge densities and potential distributions on patterned dielectric surfaces at the micronscale or larger. However, as device feature sizes shrink into the nanometer scale regime, the influence of an individual charge transferred to the surface will be larger, leading to an increase in the variability of potentials within the charging area. This leads to the question of whether a true steady-state-like behavior will be reached for high aspect ratio dielectric structures with small absolute dimension or will large oscillations in potential lead to essentially stochastic behavior. This project aims to investigate the potential stochastic behavior of differential surface charging of nanopatterned dielectric materials during plasma exposure. The improved understanding of differential charging on the nanometer length scale greatly assists in explaining and predicting the complex behavior of surface charging and subsequent surface modifications of nanopatterned dielectric materials. This also provides valuable guidance on developing plasma techniques for the fabrication of future nanostructure-based devices in electronic, photonic, chemical, and biological applications.

§ J.A. Kenney, E. Paek, and G.S. Hwang, “Stochastic Plasma Charging of Nanopatterned Dielectric Surfaces,” IEEE Trans. Plasma Sci. 36, 878 (2008).

§ J. Kenney and G.S. Hwang, “Prediction of stochastic behavior in differential charging of nanopatterned dielectric surfaces during plasma processing,” J. Appl. Phys. 101, 44307 (2007).