Invited Paper PS2-TuA9
Independent Control of Ion Energy and Flux in CCPs by the Electrical Asymmetry Effect

Tuesday, October 19, 2010, 4:40 pm, Room Galisteo

Technical plasmas are often generated by radio-frequency (RF) fields in the MHz regime. In particular, capacitively coupled RF plasmas have found wide industrial application ranging from semiconductor etching to thin film deposition as e.g. in large area production of solar-cells. In all cases the processes on the substrate surface are critically dependent on the energy and flux of the impinging ions. Therefore, independent control of these parameters is the major aim of various alternative concepts developed in the past. Despite some general progress, in practice independent control has been realized only within certain constrains.

The recently invented electrical asymmetry effect provides a novel solution by adjusting as a control parameter the relative phase between two harmonic RF frequencies [1]. This meets not only the above requirements in an almost ideal way but allows in addition for the first time breaking the symmetry in geometrically geometric discharges, which are common in large area processing. There the phase can be set so that the ion energy is increased on one electrode and reduced on the other or vice versa. The physics of the resulting non-linear system can be reduced to a few basic principles that allow an analytic treatment. The results of the analytical model are compared with particle-in-cell (PIC) / Monte Carlo (MC) simulations and experiments [1-6]. Although the system is characterized by a high degree of complexity all three approaches show remarkable agreements. Ultimately this leads to a detailed understanding not only of the dynamics of the electrical asymmetry effect but also of the physics of capacitively coupled plasmas in general.

Finally, first applications in industry on thin-film solar-cell production demonstrate superior performance by immediately more than doubling the deposition rate of silicon without loss in quantum efficiency.

References:

[1] Brian G. Heil, U. Czarnetzki, R. P. Brinkmann, T. Mussenbrock, Journal of Physics D: Applied Physics. 42, 165202 (2008)

[2] Z. Donkó, J. Schulze, B.G. Heil and U. Czarnetzki, Journal of Physics D: Applied Physics 42, 025205 (2009)

[3] Z. Donkó, J. Schulze, U. Czarnetzki, and D. Luggenhölscher, Applied Physics Letters 94, 131501 (2009)

[4] J. Schulze, E. Schüngel and U Czarnetzki, Journal of Physics D: Applied Physics 42, 092005 (2009)

[5] J. Schulze, E. Schüngel, U. Czarnetzki and Z. Donkó, Journal of Applied Physics 106, 063307 (2009)

[6] J. Schulze, E. Schüngel, Z. Donkó, and U. Czarnetzki, Journal of Physics D: Applied Physics, in print (2010)