Charging damage to gate oxides in an O2 magnetron plasma

A model is developed to explain how plasma etching/ashing can damage gate covered oxides via plasma nonuniformity. In addition, the role of antenna structure parameters on this damage is examined. Plasma nonuniformity leads to a local imbalance between electron and ion currents from the plasma. This imbalance of local particle currents from the plasma leads to gate charging and subsequent thin oxide degradation. This article discusses a sheath model for this charging where measurements of plasma potential nonuniformity are used to calculate the peak surface charging potential and subsequent thin oxide tunneling current. It is this oxide tunneling current that generates the surface states at the Si/SiO2 interface and the trapped charge in the oxide that degrades oxide yield and reliability. This model is applied to analyze oxide damage in an O2 magnetron plasma, via the simulation program with integrated circuits emphasis, Langmuir probe measurements, and antenna capacitor breakdown measurements. The oxide current derived from this model shows good agreement with experimental damage data of antenna capacitors. Finally, oxide damage is shown to depend on antenna structure parameters and is explained by this model.