Pulsed inductively coupled chlorine plasmas in the presence of a substrate bias

Pulsed inductively coupled plasmas (ICPs) sustained in electronegative gas mixtures using a substrate bias are being investigated to achieve improved etching characteristics in microelectronics fabrication. Experiments have shown that electron temperatures in pulsed ICPs without a substrate bias monotonically decrease during the afterglow. Under select conditions with a substrate bias, electron temperatures increase in the late afterglow. These trends suggest a transition in power deposition from inductive to capacitive. To investigate these processes, a two-dimensional, computationally parallel model was developed for pulsed ICPs. Results for Cl2 plasmas indicate that with a substrate bias the sheath thickness and speed, and hence electron heating, increase during the afterglow as the electron density decays. When the sheath reaches a critical thickness, capacitive electron heating begins.