Atomic-Scale Cellular Model and Profile Simulation of Si Etching: Analysis of Profile Anomalies and Microscopic Uniformity

Reactive ion etching (RIE) has been used in the manufacture of semiconductor integrated circuit devices. However, the formation mechanisms of profile anomalies and microscopic uniformity have been poorly understood until now. In this paper, we focus on the analysis of formation mechanisms of profile anomalies and microscopic uniformity during plasma etching of Si in Cl 2 plasmas, using our own atomic-scale cellular model (ASCeM). The numerical results indicated that high neutral-to-ion flux ratios result in microtrench formation. Moreover, RIE lag tends to occur at low neutral-to-ion flux ratios (<50), whereas inverse RIE lag occurs at high neutral-to-ion flux ratios in typical low-pressure and high-density plasmas. In particular, the etch rates for narrow patterns (<70 nm) increase significantly with increasing neutral-to-ion flux ratio. The synergistic effects between ion-enhanced etching and neutral shadowing in microstructural features play a significant role in the formation of profile anomalies.