Characterization of a transformer-coupled remote plasma source chamber using a fluids-based, multiphysics plasma model

The importance of remote plasma source (RPS) devices in semiconductor and thin-films manufacturing processes is growing rapidly. RPS's are found not only in subsidiary process like chamber clean or PFC abatement, but they are also being used more frequently in high-precision, primary manufacturing steps such as selective-etch or PECVD enhancement. As the application space for RPS's expands, so do the requirements placed on these devices. A new remote, transformer-coupled plasma (TCP) source with a toroidal chamber design is being developed with the intention of providing high flow rates of fluorine and oxygen based feedgases with optimized performance. An iterative design approach based solely on experimental data is crippled by long lead-times and laboratory resource availability. Thus, the goals of the present work are to use numerical modeling to characterize the plasmas within the RPS chamber and use the simulation results to optimize some of the fundamental design parameters. A "global model" of NF3 plasma is used to determine a simplified yet relevant set of reactions and collisions; then a full, 3D, steady-state model of the plasma is solved. Commercial modeling software, CFD-ACE+, was used for simulations of the plasma chamber to address gas flow, heat transfer, plasma chemistry and electromagnetics in a coupled fashion. Numerical results are correlated to experimental data, including Langmuir probe data. Then, the model is run parametrically with varying chamber topologies, to study the resulting plasma characteristics and the effect to feedgas dissociation efficiency. There is scarcity of plasma modeling in the literature for low-temperature, industrial plasmas in 3D, toroidal, transformer-coupled plasma chambers. It is the intention of the current work to elucidate both the challenges and efficacy of plasma modeling for these types of RPS devices.