Oxide damage from plasma charging: breakdown mechanism and oxide quality

The plasma-induced charge damage to small gate area MOS capacitors is investigated by using “antenna” structures. Here, we focus on the oxide defect characterization in a single wafer asher, and the role of oxide quality in a parallel plate etcher. The observed damage includes early breakdowns, excessive leakage current, an increase in interface states, and a decrease in charge-to-breakdown value. Moreover, annealing and polarity results support a hole trapping model for damage. In addition, it was found that the percentage of breakdown failure increases as the oxide quality decreases, In particular, the observed damage can increase up to 30 times when the initial oxide is degraded before plasma exposure according to how the oxide is prepared and annealed. This is important since it helps to explain how different process steps interact to affect the final yield. For instance a previous plasma process step may degrade an oxide and make it much more susceptible to damage by a subsequent plasma step