作者：Cavallotti, C.;

作者单位：Department di Chimica Materiali e Ingegneria Chimica G. Natta, Politecnico di Milano, Via Mancinelli 7, 20131 Milano, Italy

刊名：Chemical vapor deposition

ISSN：0948-1907

出版年：2010-01-05

卷：16

期：41194

起页：329

止页：335

分类号：TQ175

语种：英文

关键词：Coupled cluster;Hydrogen;Hydrogen chloride;Silicon;Surface reactions;

内容简介

The desorption of hydrogen and hydrogen chloride from Si surfaces is the rate-determining step of the low temperature CVD of silicon from both hydrogenated and chlorinated precursors. Thus, in order to model the deposition process, the rate of these reactions must be known to a high level of accuracy. In this work, the surface desorption kinetics of H_2 and HCl from the Si(100)2a? - a1 surface is investigated by modeling the surface through clusters of various dimensions (up to 60 Si atoms) and determining the reaction energies at the B3LYP, and coupled cluster methodology with inclusion of single, double and a perturbative estimation of triple excitations (CCSD(T)) levels. The investigated mechanisms are the pairwise intradimer and the 4H-2H reaction pathways. The desorption activation energy (57.4akcalamol~(-1)) and adsorption barriers (15.9akcalamol~(-1)) calculated for H_2 for the 4H and 2H pathways are in good agreement with experimental data, confirming that these are the H_2 main desorption and adsorption routes. The reaction mechanism of HCl is different to that of H_2. The calculations in fact indicate that the less activated desorption pathway (65. 0akcalamol~(-1)) is the intradimer mechanism, followed by the 2H pathway (67.1akcalamol~(-1)), which might thus compete with the intradimer pathway at low surface coverage. The HCl adsorption barrier on Si dimers is small (0.6a-a4.8akcalamol ~(-1)), confirming the high reactivity of HCl with Si surfaces. The adsorption and desorption kinetics of hydrogen and hydrogen chloride on a silicon surface were computationally investigated using density functional and coupled cluster theories. The investigated mechanisms were the pairwise intradimer and the 4H-2H reaction pathways. The calculations reveal that, while the H_2 surface desorption dynamics is dominated by the 4H-2H mechanisms, the fastest HCl desorption mechanism proceeds through the intradimer pathway.