Electron beam induced deposition: A surface science approach

It has become increasingly difficult to adapt current technologies of integrated circuit nanofabrication to ever increasing demands for smaller deposition resolution. Immersion lithography, a method of photolithography, is the current generation of large scale production technology for the fabrication of these devices; though it is theorized that photolithography is simply unable to generate structures smaller than 16 nanometers. Fortunately, electron beam induced deposition (EBID) of volatile precursors has emerged as an effective and versatile method for creating two and three-dimensional nanostructures. However, the range of applications for materials deposited from organometallic precursors is often limited by the unacceptably high level of organic contamination present. To improve control over the deposition process, it is necessary to better understand the fundamental molecular level processes associated with EBID. This doctoral thesis addresses the need for a detailed investigation of the electron stimulated decomposition process by using traditional surface chemistry techniques to probe the EBID process in situ and in real-time.;Contrary to most EBID studies, the molecular precursors in this thesis have been molecularly adsorbed onto inert surfaces under ultra high vacuum conditions. These molecular films were then irradiated with low energy electrons (40-3000 eV) and probed using surface chemistry techniques. Results from these studies revealed new ways of calculating the total reaction cross-sections for molecules undergoing electron induced decomposition at surfaces. Two organometallic precursors, trimethyl(methylcyclopentadienyl) platinum(IV) and dimethyl-(acetylacetonate) gold(III), were found to decompose as a result of an electron initiated bond cleavage event between the metal center and a methyl ligand. These studies provide new insight into the role of the organometallic precursor ligand architecture during the EBID process. In addition, post-deposition purification using atomic hydrogen and atomic oxygen was found to successfully remove 100% of organic contamination from EBID deposited films.;Growth of amorphous carbon-nitride films from 1,2-diaminopropane using EBID was also investigated. It was found that the electron stimulated dehydrogenation of the organic precursor induces formation of nitrile bonds and that the stoichiometry of the precursor is preserved in the product. Systematic variation in the incident electron energy revealed that the deposition proceeds with maximum efficiency when exposed to 200 eV electrons, a similar energy dependence was found for the electron simulated decomposition of organometallic precursors.