This talk will present the mechanism, kinetics, and potential applications associated with the vapor phase deposition of functional polymers onto structured materials and liquid surfaces. Vapor phase deposition eliminates the need for organic solvents and thereby offers a safer and cleaner alternative to liquid phase polymer processing. We will demonstrate our ability to pattern functional polymers onto structured materials such as microfluidic devices, porous materials, and pillar arrays. We will also present our recent work demonstrating deposition onto liquids with negligible vapor pressures such as ionic liquids (ILs) and silicone oils. We will demonstrate that the polymer morphology at the liquid/vapor interface is controlled by surface tension interactions. The ability to controllably tailor polymer morphology at the interface allows for the design of ultrathin free-standing polymer films, micron-scaled particles, and core-shell particles. We will also demonstrate that polymerization can occur within the liquid layer allowing for the fabrication of polymer/IL composite films.

An innovative surface wave plasma source provided by Starfire Industries, LLC has been tested by the Center for Plasma-Material Interactions at the University of Illinois Urbana-Champaign. Operating in the microwave range, the source efficiently generates high-density (10^11~12 cm^-3) and low electron temperature (~1 eV) plasmas. Thin silicon films were deposited with the interest of characterizing a cost-effective PECVD process for high quality silicon photovoltaics. Parameters of interest included substrate temperature, total operating pressure, silane dilution, RF power, discharge gap width, and process gas flowrate. Through a SiH₄:H₂ discharge, films were deposited and subsequently analyzed via profilometry, SEM, Raman microscopy, and X-ray diffraction. For a 15 cm source, consistent radial uniformity was maintained across a 12 cm diameter from 2.0±0.4 nm/s up to 3.5±0.9 nm/s at a 2.5 cm discharge gap. Well-formed films were produced with substrate temperatures above 285C. With decreasing operating pressure and increasing flowrate, area of coverage is shown to increase without compromising speed of film growth. An assessment on deposition rate optimization, film uniformity, and large-area scalability is presented.

Silicon nitride films are well known as important dielectric components for semiconductor device fabrication because of their good physical and electrical properties for 3D structure device construction. High quality silicon nitride film deposition has been demonstrated in high density plasma sources by using RLSA^TM in which a nitrogen and hydrogen containing plasma nitrates a silicon surface deposited by a thermal adsorption process. [1] A typical precursor for the silicon component is Dichlorosilane (DCS), used in thermal CVD of silicon nitride. [2] In plasma assisted atomic layer deposition of silicon nitride films, silicon nitride deposition is effected by alternating deposition and nitridation steps. The film quality, defined by the 0.5% DHF solvent wet chemical etching ratio, is a function of many process parameters. It has been shown experimentally that hydrogen radicals produced in this plasma are important for film quality. The exact film growth mechanism in plasma assisted deposition processes is, as yet, not fully clarified and most studies are related to thermal CVD. Ab-initio studies focusing on the role of radicals are rare. In this presentation a quantum chemistry analysis (Gaussian 09) of the film formation mechanism in Atomic layer Deposition sequence is presented. Hexachlorodisilane (HCD) is used as a model surface in the study. We revealed the role of H as a critical precursor for the growth of high quality films. Un-dissociated ammonia or hydrogen interacts with Si-Cl to liberate chlorine from silicon. Hydrogen liberates H from the new NH₂ structure. Silicon containing structures with dangling bonds interact with the structure then complete the formation of Si-N-Si bonding. Hydrogen and NH_x limit restoration of the Si-Si chain.