AVS 46th International Symposium
    Manufacturing Science and Technology Group Thursday Sessions
       Session MS+PS-ThM

Paper MS+PS-ThM8
Modeling of Nonisothermal, Coupled Neutral/Plasma Dynamics in PFC Abatement Plasmas

Thursday, October 28, 1999, 10:40 am, Room 611

Session: Environmentally Benign Manufacturing
Presenter: M.W. Kiehlbauch, University of California, Berkeley
Authors: M.W. Kiehlbauch, University of California, Berkeley
A. Fiala, University of California, Berkeley
E.J. Tonnis, University of California, Berkeley
D.B. Graves, University of California, Berkeley
Correspondent: Click to Email
Reducing PFC emissions is an area of increasing concern in semiconductor manufacture. One method of PFC emission reduction is through the use of point-of-use (POU) plasma abatement. In POU plasma abatement, an oxidizing species such as O@sub 2@ or H@sub 2@0 is added to the process tool effluent in the tool foreline. A plasma in the foreline is then used to convert PFCs to oxidized, wet-scrubbable species. Abatement plasmas can be used to reduce PFC emissions from oxide etch and in-situ CVD chamber clean processes and several commercial tools have been designed for these applications. Additionally, the abatement plasma structure is similar to downstream plasma sources which are increasingly used in chemical downstream etch and remote CVD chamber clean. A two-dimensional, coupled plasma and neutral model has been developed and applied to CF4/O2 and C2F6/O2 POU plasma abatement. The neutral model solves the overall neutral mass, momentum and energy balances. Additionally, the species mass balances are solved, together with a rigorous multi-component diffusion formulation. The neutral model is coupled via collisional terms to an INDUCT95 plasma model. The model allows the resolution of neutral temperature profiles and species concentration profiles. At high plasma powers, the neutral mean molecular weight decreases by ~ 50% while the neutral temperature increases by ~ 400%. The resulting density and velocity gradients have a major impact on the plasma structure and the composition of the gas flow leaving the plasma zone. We will present results that show these effects for various PFCs, power deposition profiles, flow rates, pressures and plasma powers. The relative importance of advective and diffusive transport will be considered. Additionally, the effect of wall temperature on the plasma structure will be investigated. Model results will be compared to those obtained experimentally. The application of these results to downstream plasma sources will be discussed.