INELASTIC-SCATTERING DYNAMICS OF HYPERTHERMAL FLUORINE-ATOMS ON A FLUORINATED SILICON SURFACE

The interaction of energetic fluorine atoms with a fluorinated silicon surface has been studied by monitoring energy and angular distributio ns of scattered fluorine atoms. Two beams with average translational e nergies of 284 and 544 kJ/mol were directed onto the SiFx layer, known to exist during steady-state etching. While thermal scattering of unr eacted fluorine atoms is observed, nonthermal scattering dominates and includes both single- and multiple-bounce collisions at the complex s urface. Multiple-bounce collisions often lead to a near-thermal (cosin e) distribution of exit angles but incomplete thermalization of transl ational energy. A hard-sphere kinematic model, based on single atom-su rface collisions, can be used to predict the overall average energy tr ansfer as a function of deflection angle, indicating that the complex scattering events at the surface can appear on average like single col lisions.