Consequences of secondary electron emission on charging of SiO2 features in capacitively coupled plasmas having sinusoidal and tailored bias waveforms

In plasma etching of dielectric materials for microelectronics fabrication, energetic ions with narrow angular distributions preferentially positively charge the bottom of features, while isotropic electrons preferentially charge the top negatively. This process generates intrafeature electric fields that can distort the trajectories of charged particles leading to defects. Remedies to alleviate charging include using voltage-waveform tailoring (VWT) to produce electron fluxes having higher energies and narrower angular distributions to better neutralize positive charge. One phenomenon relevant to the charging process is secondary electron emission (SEE), in which one or more electrons are emitted upon particle impact. In this work, we computationally investigated the dynamics of charging of high aspect ratio features in capacitively coupled plasmas sustained in argon. Charging of preformed features is discussed to better disconnect the evolution of the feature from charging dynamics. We found that SEE redistributes charge within the feature, lowering the in-feature positive electric potential and altering the electric potential profile. The reduction in potential is largest when the degree of SEE is the highest. The effectiveness of VWT to increase electron energies and narrow angular distributions in remediating charging was also investigated. We found that when including SEE, anisotropic electrons become less able to remediate charging as the potential in the feature is dominated by charge redistribution.