SIMULATION OF A SURFACE-REFLECTION NEUTRAL STREAM SOURCE

We have developed a computational model to optimize the design of a su rface reflection neutralization source of hyperthermal neutrals for ch arge-free processing. For the deployment of this technique to producti on (greater than or equal to 8 in. wafers) processing, a system design study has been completed. A Monte Carlo model is used to determine th e energy and angular distributions of reflected hyperthermal neutrals at the surface of a wafer, as well as flux uniformity. A simple form f or the plasma profile is chosen to allow simulation of various profile s reported in the literature. Neutrals are launched from the reflector consistent with the relative plasma density at each position on the r eflector with angular and energy distributions consistent with experim ental observations. These neutrals are then followed through interacti ons with thermal background atoms and the plasma. Charge exchange, ion ization, and elastic scattering processes are considered for argon as the main feedstock gas. The results show the trade off between a high density plasma for substantial wafer neutral flux and losses of the ne utral stream due to ionization and charge exchange in the plasma strea m. (C) 1996 American Institute of Physics.