Plasma-Enhanced Chemical Vapor Deposition (PECVD) is a popular technique used to grow amorphous, nanocrystalline, and crystalline Si films. Thanks to the high reactivity of radicals and ions produced by the plasma interaction with silane molecules, high growth rates and relatively low growth temperatures can be achieved. In spite of the availability of a huge experimental data set, many of the key parameters controlling
typical film properties are still in need of theoretical investigation. Here we focus our attention on the impacts of typical radicals (SiHx, x=1,2,3) and of atomic hydrogen with a crystalline Si(001) surface at typical growth conditions. By using a synergic combination of accurate Car-Parrinello molecular dynamics simulations and of simpler
classical-potential runs, we are able to quantify the relative importance of several processes such as hydrogen removal [1], adsorption of the impinging molecules on the surface, and hydrogen-induced adsorbed radicals etching. The role played by the above atomic-scale mechanisms in influencing the growth rate and the crystallinity of the film is discussed, as well as the possibility of building a more macroscopic model taking into account surface kinetics and gas-phase reactions.
[1] S. Cereda, M. Ceriotti, F. Montalenti, M. Bernasconi, and L. Miglio
(2007, submitted) |