Specialized design for three basic mask patterns counteract charging effects during plasma etching

Abstract

In the plasma etching technique, effectively suppressing charging effects is crucial for achieving a high-quality transfer of the mask pattern onto the substrate. For instance, mask patterns that combine complex shapes frequently exhibit a noticeable “corner effect,” characterized by significant variations in physical quantities at locations where curvature changes rapidly. This study investigates the feasibility of utilizing specialized designs for mask holes with three basic-shaped openings to counteract charging effects. The research focuses on isolated and deformed triangular, square, and hexagonal mask holes as well as two types of mask arrays (quadrangle and hexagonal arrays). A classical particle simulation program was employed to analyze the evolution of electric field (E-field) distribution and simulated opening during etching time. The results indicate that ions preferentially bombard the sides rather than the vertexes, resulting in flattening of deformed sides. As expected, approximately triangular, square, and hexagonal etched openings can be achieved. Unlike an isolated mask hole, the design for a hole in a specific array is constrained by the pattern of the array. Simulated evolutions demonstrate that specialized designs based on specific arrays can assist in obtaining nearly perfect etched openings. Possible underlying mechanisms have been extensively discussed in this study. These findings offer potential insights into specialized designs for basic mask patterns to counteract charging effects, thereby contributing toward maintaining pattern integrity.