AVS 49th International Symposium
    Plasma Science Thursday Sessions
       Session PS+TF-ThM

Paper PS+TF-ThM10
On the Roughness Evolution during Remote PECVD of Amorphous Silicon

Thursday, November 7, 2002, 11:20 am, Room C-103

Session: Plasma Enhanced Deposition
Presenter: A.H.M. Smets, Eindhoven University of Technology, The Netherlands
Authors: M.C.M. Van de Sanden, Eindhoven University of Technology, The Netherlands
A.H.M. Smets, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The roughness evolution during the growth of hydrogenated amorphous silicon is studied in situ by means of single wavelength ellipsometry. The roughness measurements are corroborated by ex situ spectroscopic ellipsometry and Atomic Force Microscopy on films having thickness in the range from 30 up to 3000 nm. The films were deposited by means of the expanding thermal plasma, a remote plasma technique. Silane is injected downstream in an Ar/H@sub 2@ plasma. From detailed measurements in the gas phase it is established that the dominant radical contributing to the film growth is the silyl radical with minor contributions from other radicals such as Si, SiH and H. The self-bias is small which characterizes the a-Si:H growth from this dominantly SiH@sub 3@ source as purely chemical in origin. The roughness evolution is analysed by means of the scaling properties of the surface as first proposed by Family and Vicsek.@footnote 1@ It is found that the surface width scales with film thickness d as d@super ß@. @beta@, the dynamic scaling exponent, is determined as function of substrate temperature and growth rate. A cross-over from random deposition (@beta@ = 1/2) at low substrate temperatures, to a deposition process in which surface diffusion dominates the roughness evolution is observed. The scaling universality class of the roughness development of the growth of a-Si:H shows great similarity with, e.g., Molecular Beam Epitaxy of crystalline silicon. The activation energy from beta vs. substrate temperature is determined from comparing the data with a solid-on-solid model and is about 1 eV. This value is much higher than expected on basis of the conventional growth models for a-Si:H, in which the weakly adsorbed SiH@sub 3@ radical is assumed to rule the roughness evolution. The implications for the growth model of a-Si:H will be discussed. @FootnoteText@ @footnote 1@ F. Family and T. Vicsek, J. Phys. A 18 L75 (1985).