The gain and loss of energy by electrons in the RF-CCP sheath

Abstract

The exact mechanism for the heating of electrons in the sheath of radio frequency capacitively coupled plasma (RF-CCP) discharges is poorly understood. A hybrid one-dimensional model of a RF-CCP discharge is used to study this problem by tracking electron trajectories and electron energy change in the RF-CCP sheath. This study shows that the Ohmic electric field, the field due to conduction current, can have an effect on electron heating in the plasma sheath. Both the ambipolar and the Ohmic electric field can repel low energy electrons and reduce their interaction with the changing electric field in the sheath region. A comparison is made between the more realistic Brinkmann fluid sheath model and a hard wall approximation. For energetic electrons, the hard wall approximation accurately models electron heating. However, the hard wall approximation does not accurately model the heating of lower energy electrons or allow for electron losses to the electrode. A comparison is also made between the electron energy probability function calculated using a Monte Carlo simulation with and without the effects of the sheath.