Plasma processing is ubiquitous in the electronics industry. Thin films of Si based materials, Si oxides and nitrides and newer materials like Germanium-Carbon and Silicon-Carbon alloys are used extensively in both electronics and optical industries. The properties of the materials depend critically upon exactly how the film was deposited, and what happened at the interfaces between different films. In this research program , we investigate systematically the growth of thin films under different, well controlled plasma conditions so that we can correlate the film properties with plasma deposition chemistry. On-line optical emission spectroscopy, in-line mass spectrometry and movable Langmuir probes are used to characterize the plasma, and to measure properties such as plasma potential, electron and ion energies, and the density of radicals actually arriving at the substrate. The plasma characterization tools are movable and can be used to diagnose ECR plasma ( which operates at very low pressures), VHF plasma and RF glow discharge plasma. A surprising discovery has been that, contrary to the usual model of growth, SiH3 is not the predominant radical involved in the growth of Si films. Rather, SiH radical may also play a major role in this process. Fig. 1 shows that results obtained using a mass-spectrometer in a low pressure, remote ECR silane plasma. This is a significant result, because it indicates that the properties of the films may also depend strongly upon the plasma conditions. We hope to extend this research to the growth of films from specific radicals in the future.
Fig. 1. Densities of different silane radicals measured using in-line mass-spectrometry in a remote ECR plasma. Note that the density of SiH is higher than that of SiH3 at high powers.
Faculty
Vikram Dalal
Staff
Ruth Shinar, Max Noack
Students
Kamal Muthukrishnan, Dan Pates, Dan Stieler
Papers
Funding Agencies
