Effect of Dual Radio Frequency Bias Power on SiO₂ Sputter Etching in Inductively Coupled Plasma

Dual radio frequency (RF) powers are widely used with commercial plasma etchers for various nanoscale patterns. However, it is challenging to understand the relationship among the dual RF powers and the etching processes. In this work, the effect of the dual RF bias powers on SiO₂ sputter etching was investigated in inductively coupled plasma (ICP). The relationship was studied among 2MHz and 27.12MHz RF bias powers, a 13.56MHz ICP source power, the ion bombardment energy, the ion density and the etching rate. The results show that the ion density of Ar plasma can be controlled in the region of 10^9-1011 ions/cm³, and DC self-bias can be controlled by controlling the ratio of dual RF bias powers while the ion density is maintained with the operation of source power. This work reveals that the dual RF bias powers expand the process window of the ion density and the ion bombardment energy independently in the ICP plasma source. The sputter etching rate is also modeled using the ion-enhanced etching model, and the model shows good agreement with the etching rate data.