THEORETICAL-STUDY OF MOLECULAR CONTAMINATION ON SILICON-WAFERS - KINETICS

In an earlier paper [''Theoretical Study of Molecular Contaminants on Silicon Wafers: Interactions Bent een Molecular Contaminants and the S ilicon Surface,'' Journal of the IEST, July/August 1998] a simple form ulation was developed to describe interactions between gas phase molec ules and solid surfaces.(1) Adsorption energies of various organic/ino rganic molecules on silicon wafer surfaces were derived In this paper; the relationship between the gas phase molecule concentration and the surface contamination density based on simple kinetic theories is est ablished The most important approximations in this derivation include the neglect of possible chemical reactions on the surface and the assu mption that gas phase concentrations of pollutants are constants, both in time and in location. The mass transport mechanisms are ignored. W ith these approximations, the equilibrium in surface kinetics can be r eached almost instantly for all the molecules investigated, even for t hose having activation energies as high as similar to 72 kJ/mole. This agrees with the experimental data for moisture adsorption on stainles s steel.(2) A guide is provided for material selection.