IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM4
Self-Similar Structure Evolution and Surface Reaction Kinetics in Low Temperature Silicon Deposition

Wednesday, October 31, 2001, 9:20 am, Room 123

Session: Fundamentals of Deposition
Presenter: G.N. Parsons, North Carolina State University
Authors: G.N. Parsons, North Carolina State University
K.R. Bray, North Carolina State University
A. Gupta, North Carolina State University
Correspondent: Click to Email
A current challenge in low temperature thin film deposition is to analyze energetics and kinetics of surface processes to control growth reactions and improve material properties. In this work, surface transport kinetics during silicon plasma deposition are determined by analyzing time and temperature dependent surface topography in comparison to dynamic scaling models. For plasma deposition of silicon using silane or silane/helium mixtures at 25 - 350°C, static and dynamic scaling parameters determined from atomic force microscopy are consistent with self-similar fractal geometry. Comparing parameters with those expected from linear continuum models indicates indicate that surface transport is dominated by adspecies diffusion with a diffusion activation barrier of 0.2eV, consistent with previous empirical estimates. However, the elementary steps associated with initial film growth are still not clear. The observed increase in diffusion length with increasing temperature contradicts some current published growth models, and ab-initio analysis of precursor adsorption reactions indicate that silyl radicals do not directly adsorb onto Si-H bonds to form 3-centered bonds, as is commonly proposed. When helium is replace by argon, significant departure from self-similar structure is observed, consistent with excess energy from surface bombardment of heavier Ar ions. Diluting silane with hydrogen results in significant changes in scaling coefficients, indicating that an additional non-linear term is needed in the continuum model to describe surface diffusion. All of the results suggest that atomic hydrogen generated in the plasma plays an important role in assisting surface transport. Possible elementary surface reactions consistent with observed results will be presented and discussed.