AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThP

Paper PS-ThP5
Self-Consistent Electrodynamics of Very High Frequency Plasma Discharge Chambers

Thursday, November 12, 2009, 6:00 pm, Room Hall 3

Session: Plasma Science Poster Session
Presenter: Z. Chen, Applied Materials, Inc.
Authors: Z. Chen, Applied Materials, Inc.
J.A. Kenney, Applied Materials, Inc.
S. Rauf, Applied Materials, Inc.
K. Collins, Applied Materials, Inc.
Correspondent: Click to Email
Very high frequency (VHF) radio-frequency (RF) sources are used for many plasma processing applications including material etching and thin film deposition. However, when chamber dimensions become commensurate with RF wavelength, electromagnetic effects have a significant influence on plasma behavior. We present a 2/3-dimensional model for self-consistently studying both electrodynamic and plasma dynamic behavior of complete RF plasma discharge chambers. The model is fully self-consistent in the following senses: (1) Maxwell’s equations and transport equations for charged and neutral species are coupled and solved explicitly in time domain; (2) The complete RF plasma discharge chamber including the RF power delivery sub-system, electrodes and plasma domain is modeled all together and simultaneously; and (3) The RF source is naturally applied onto the transmission line of the RF feed system in the form of an electromagnetic wave rather than hard imposition of assumed RF sources onto the electrodes or on the boundary of plasma. In the model, Maxwell’s equations are discretized using the Finite-Difference Time-Domain (FDTD) method, and plasma discharge is modeled by solving the time-dependent continuity equations for charged and neutral species, drift-diffusion approximation for specie fluxes, and the electron energy conservation equation. Such a systematic approach is equally applicable to both capacitive and inductive discharges. It is useful for understanding not only electrodynamic effects in large-area VHF plasma chambers, but also the impact of asymmetric parts in RF systems and electrodes on the symmetry and uniformity of electric field and plasma in discharge region, which is of significant interest in industrial applications of RF plasma chambers. We first apply the model to study the impact of azimuthally asymmetric dielectric and conducting perturbations in the RF feed system on plasma uniformity. Then we examine the effect of transmission line length and impedance on plasma profile, especially in regimes close to resonance. We also explore the potential application of VHF source in large area (> 5 m2) capacitively coupled plasmas. Based on the model, we have been able to identify a variety of design approaches for ensuring electric field and plasma symmetry and uniformity in discharge region.