Exploring the Impact of Mask Geometries on High Aspect Ratio Silicon Etching Using Cl₂/O₂ Plasmas

As computing technology advances, the demand for more intricate geometries in etching processes has surged, necessitating a deeper understanding of the underlying physics. While previous published computational studies predominantly focus on via and trench geometries, the challenges posed by alternative mask geometries remain largely unexplored. This study employs Monte Carlo-based feature scale simulations to investigate high aspect ratio silicon etching using Cl₂/O₂ plasma. Initially, we present the general behavior of etching features with a rectangular geometry to establish a baseline. Subsequently, we investigate the 3D etching dynamics of rectangular mask openings under varying oxygen flow rates and bias duty cycles. Increased oxygen flow enhances sidewall protection but reduces etch rate. Elevating the bias duty cycle slightly improves the etch profile but reduces selectivity due to increased high-energy ion flux. The feature scale study culminates in an analysis of the impact of mask geometry by comparing etching profiles produced with circular, square, and rectangular mask shapes. Despite identical initial opening areas, differing shapes lead to variations in etch rates, attributed to deviations from the initial geometry during etching. We are currently conducting molecular dynamics simulations to deepen our understanding of silicon etching in chlorine-oxygen environments. These simulations focus on capturing effects of varying flux ratios of radicals and ions at different energy levels. Our findings highlight the challenges of etching high aspect ratio features, emphasizing the need for simultaneous advancements in hardware and process innovations as device geometries become more complex.