Different methods for improving uniformity of very high frequency capacitively coupled discharges

Capacitively coupled discharges driven at radiofrequencies are often used for technological purposes, which involve interaction of ions emanating from plasma and subtrate or target put on electrodes. To make the processing rate larger, it is desirable to increase the corresponding ion fluxes. On of the simplest ways to increase the flux of ions impinging on the electrodes is to use a higher driving frequency. However, this may lead to radial nonuniformities of the ion flux and/or average energy. Employing a fully electromagnetic implicit energy- and charge-conserving code ECCOPIC2M, in this work we investigate different methods for improving the radial uniformity of the mentioned discharge properties in capacitively coupled discharges driven at very high frequencies. In particular, we consider using an axial magnetic field, multiple frequency harmonics, and an external network suppressing high frequency harmonics in the discharge current.