Low-temperature plasma physics and technology are diverse and interdisciplinary fields. The plasma parameters can span many orders of magnitude and applications are found in quite different areas of daily life and industrial production. As a consequence, the trends in research, science and technology are difficult to follow and it is not easy to identify the major challenges of the field and their many sub-fields. Even for experts the road to the future is sometimes lost in the mist. Journal of Physics D: Applied Physics is addressing this need for clarity and thus providing guidance to the field by this special Review article, The 2012 Plasma Roadmap. Although roadmaps are common in the microelectronic industry and other fields of research and development, constructing a roadmap for the field of low-temperature plasmas is perhaps a unique undertaking. Realizing the difficulty of this task for any individual, the plasma section of the Journal of Physics D Board decided to meet the challenge of developing a roadmap through an unusual and novel concept. The roadmap was divided into 16 formalized short subsections each addressing a particular key topic. For each topic a renowned expert in the sub-field was invited to express his/her individual visions on the status, current and future challenges, and to identify advances in science and technology required to meet these challenges. Together these contributions form a detailed snapshot of the current state of the art which clearly shows the lifelines of the field and the challenges ahead. Novel technologies, fresh ideas and concepts, and new applications discussed by our authors demonstrate that the road to the future is wide and far reaching. We hope that this special plasma science and technology roadmap will provide guidance for colleagues, funding agencies and government institutions. If successful in doing so, the roadmap will be periodically updated to continue to help in guiding the field.

Inductively coupled plasmas (ICPs) are currently being investigated as high density (> lo"-10" cmB3), low pressure (< l-20 mTorr) sources for semiconductor etching and deposition. We have developed a two-dimensional (Y,z) hybrid model for ICP sources and have used the model to investigate Ar/C!Fd02 mixtures for etching applications. The simulation consists of electromagnetic, electron Monte Carlo, and hydrodynamic modules with an "off-line" plasma chemistry Monte Carlo simulation. The model produces the temporally and spatially dependent magnetic and electric fields (both inductively and capacitively coupled), plasma densities, and the energy resolved flux of ions and radicals to the substrate. We discuss-results for densities, power deposition, and ion energies to the substrate as a function of position.

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Capacitively coupled radio-frequency (rf) glow discharges are standard sources in plasma assisted materials processing. Theoretical analyses of rf discharges have been hampered by the computational difllculty of simultaneously resolving nonequilibrium electron transport and plasma chemistry. We have developed a hybrid Monte Carlo-fluid simulation that can simulate nonequilibrium electron transport while executing with the speed of a fluid simulation. An electron Monte Carlo simulation (EMCS) is used to calculate the electron energy distribution (EED) as a function of position and phase in the rf cycle. Collision rates and transport coefficients are calculated from the EED and used in a selfconsistent fluid model (SCFM) of charged particle behavior and a neutral chemistry/transport model. Electric fields from the SCFM are cycled back to the EMCS, and the process is iterated until convergence. All pertinent heavy particle (charged and neutral) reactions can be included as well as collisions of electrons with ions, excited states, and reaction prod&s. The hybrid model is applied to a variety of gas mixtures of interest to materials processing. 1654

The left branch of the Paschen curve for helium gas is studied both experimentally and by means of particle-in-cell/Monte Carlo collision (PIC/MCC) simulations. The physical model incorporates electron, ion, and fast atom species whose energy-dependent anisotropic scattering on background neutrals, as well as backscattering at the electrodes, is properly accounted for. For the range of breakdown voltage 15 kV V br 130 kV, a good agreement is observed between simulations and available experimental results for the discharge gap d ¼ 1.4 cm. The PIC/MCC model is used to predict the Paschen curve at higher voltages up to 1 MV, based on the availability of input atomic data. We find that the pd similarity scaling does hold and that above 300 kV, the value of pd at breakdown begins to increase with increasing voltage. To achieve good agreement between PIC/ MCC predictions and experimental data for the Paschen curve, it is essential to account for impact ionization by fast atoms (produced in charge exchange) and ions and for anisotropic scattering of all species on background atoms. With the increase of the applied voltage, energetic fast atoms progressively dominate in the overall ionization rate. The model makes this clear by predicting that breakdown would occur even without electron-and ion-induced ionization of the background gas, due to ionization by fast atoms backscattered at the cathode, and their high production rate in charge exchange collisions. Multiple fast neutrals per ion are produced when the free path is small compared to the electrode gap. Published by AIP Publishing.