IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Tuesday Sessions
       Session PS2+TF+SE-TuA

Paper PS2+TF+SE-TuA8
An In Situ Study of the Interactions of Atomic Deuterium with Hydrogenated Amorphous Silicon Thin Films Using Multiple Total Reflection Fourier Transform Infrared Spectroscopy

Tuesday, October 30, 2001, 4:20 pm, Room 104

Session: PECVD/IPVD
Presenter: S. Agarwal, University of California, Santa Barbara
Authors: S. Agarwal, University of California, Santa Barbara
A. Takano, Fuji Electric Corporate Research and Development, Ltd., Japan
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
D. Maroudas, University of California, Santa Barbara
E.S. Aydil, University of California, Santa Barbara
Correspondent: Click to Email
Atomic hydrogen plays a crucial role in the deposition of amorphous hydrogenated silicon (a-Si:H) from silane containing discharges which are often diluted with hydrogen. However, during the deposition process the role of atomic hydrogen cannot be isolated from the other radicals impinging onto the surface. In order to isolate the effect of H atoms, as deposited a-Si:H films were exposed to a deuterium plasma and subsequent compositional and structural changes in the film were studied using in situ multiple total reflection Fourier transform infrared (MTR-FTIR) spectroscopy. The use of atomic deuterium generated by the plasma allowed us to observe both the abstraction-passivation reaction and the insertion reaction since the stretching modes of SiH@sub x@ (x = 1,2,3) and SiD@sub x@ (x = 1,2,3) appear at different wavenumbers. a-Si:H thin films were deposited in an inductively coupled plasma reactor at 200 °C. The deposited films were exposed to a series of one second deuterium plasma pulses at different substrate temperatures. In situ MTR-FTIR was used to observe the changes in the film after each pulse. Peak assignments were made and the IR data was deconvoluted for both the SiH@sub x@ and SiD@sub x@ part of the spectrum. Removal of surface hydrides is very fast and there is no activation barrier for the abstraction-passivation reaction in agreement with atomistic calculations of this barrier. The modification of the bulk film through abstraction and insertion reactions is limited by diffusion of D. Moreover, we find evidence for the presence of a thin sub-surface region (<30 Å) that has a higher concentration of silicon di- and trihydrides and strained silicon-silicon bonds. Insertion into the Si-SiH@sub2@ bonds in this layer is faster than insertion into Si-SiH.