Effect of mask geometry on high aspect ratio silicon etching using Cl2/O2 plasma

Abstract

The relentless growth in computational demands has driven substantial advancements in microelectronic device architectures in recent years. Three-dimensional (3D) structures are now predominant in leading edge logic and memory integrated circuits. These developments pose significant challenges in etching and deposition processes due to the complexity of the 3D geometries. This study focuses on Si etching in an inductively coupled Cl2/O2 plasma. A Monte Carlo-based 3D feature-scale model is used to investigate how the initial mask geometry and operating conditions affect 3D etching profiles. The etching behavior associated with a rectangular mask opening is first examined, highlighting the trade-offs inherent during process development. The impact of initial mask shape on etching outcomes is also explored by comparing the etched profiles across masks with rectangular, square, and circular openings. Despite identical opening areas, these geometries exhibit significant variations in etch characteristics. Through the cases presented, we underscore the process challenges posed by etching 3D features with high aspect ratios, in both the vertical and lateral directions.