| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Friday Sessions |
| Session PS-FrM |
| Session: | Plasma Modeling |
| Presenter: | Xiaopu Li, Applied Materials |
| Authors: | X. Li, Applied Materials K. Bera, Applied Materials S. Rauf, Applied Materials K.S. Collins, Applied Materials |
| Correspondent: | Click to Email |
Capacitively coupled plasmas (CCP) are widely used for semiconductor material processing. One usually strives to obtain uniform fluxes of active neutrals and ions and ion energies at the substrate for optimum process uniformity. As technology is accelerating, advanced processing application requires not only uniformity but also flexible control of species fluxes and energies. Recently, electrical asymmetric effect (EAE) has been extensively studied in the literature [1-3], where separate control of ion flux and ion energy is achieved by applying a fundamental frequency and its higher harmonics in a high frequency CCP source. In the present study, EAE is systematically investigated by tailored-waveform excitations in the very high frequency (VHF) regime where electromagnetic effect becomes significant. A fully coupled electromagnetic plasma model is used to consider both EAE and electromagnetic effects. The fluid plasma model computes species densities and fluxes, as well as the plasma current density. Drift-diffusion approximation is used for species fluxes in the continuity equations for all charged species. Neutral species densities are determined by solving the continuity equations with diffusion coefficients computed using the Lennard-Jones potentials. The electromagnetic phenomena are described by the Maxwell equations with the plasma current density updated from the fluid model. The finite difference time domain (FDTD) technique is used to discretize the Maxwell equations, which are solved explicitly in time. A geometrically asymmetric discharge is excited using the VHF source and its harmonics. The phase between the excitation frequency and its harmonics has been modulated to control the electrical asymmetry. Ar discharge is studied based on the reaction mechanism similar to the previous study [4]. This study provides a fundamental understanding of EAE, that is important to achieve flexible control of ion fluxes and energies in VHF capacitively coupled plasmas.
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2. E. Schüngel et al, J. Appl. Phys. 112, 053302 (2012)
3. T Lafleur, 2016 Plasma Sources Sci. Technol. 25 013001 (2016)
4. S. Rauf and M. J. Kushner, J. Appl. Phys. 82, 2805 (1997)