AVS 47th International Symposium
    Manufacturing Science and Technology Thursday Sessions
       Session MS-ThA

Paper MS-ThA7
First Principles Modeling of Gas-Surface Interactions in Low Pressure CVD Processes

Thursday, October 5, 2000, 4:00 pm, Room 304

Session: Advanced Modeling for IC Manufacturing
Presenter: H. Simka, Intel Corp.
Authors: H. Simka, Intel Corp.
S.S. Shankar, Intel Corp.
J.-R. Hill, Molecular Simulations, Inc.
S. Mumby, Molecular Simulations, Inc.
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Understanding and optimization of low-pressure CVD systems typically necessitate knowledge of interactions between gas-phase species and surface at the molecular level. A physically-based approach to model these interactions is presented. The approach is based on ab-initio quantum chemistry investigations of molecular and surface properties, as well as binding between reactive gas-phase precursors with atoms on the growth surface. Application of the method to low-pressure CVD of silicon nitride using dichlorosilane (DCS) and ammonia will be illustrated. Energetics of the gas-surface interactions are calculated using density-functional theory (DFT), with the surface represented by H-terminated clusters involving the active centers. Energy values obtained using DFT methods for this system are typically more accurate compared to those obtained using semi-empirical methods. For example, the activation barrier for gas-phase decomposition of DCS to SiHCl and HCl calculated using the PM3 semi-empirical method is 45 kcal/mole, which is significantly lower than values obtained using DFT and more accurate ab-initio methods such as G2 (65 to 68 kcal/mole). Other comparisons illustrating further limitations of the semiempirical method for modeling of gas-surface interactions will be presented. Reactivity of several surface sites in the cluster model is investigated. Adsorption energies of several gas-phase species are calculated; accuracy of the several DFT methods used is evaluated and will be discussed.