Edge placement error analysis through backscattered electron imaging

Edge placement error (EPE) has become a critical metric for ensuring patterning accuracy and optimizing the process window in semiconductor manufacturing. Initially introduced to measure optical proximity correction (OPC) errors, EPE now encompasses a broader set of parameters, including overlay (OV), critical dimension uniformity (CDU), and line width roughness (LWR), making it essential for managing the complexity of advanced multi-patterning processes. Despite its importance, directly measuring EPE remains challenging due to the intricate nature of modern semiconductor devices, often requiring statistical methods for estimation. This paper demonstrates the use of secondary electron (SE) and backscattered electron (BSE) imaging to improve the accuracy and practicality of EPE measurement. By optimizing BSE imaging conditions, layers such as contact and can be visualized simultaneously, allowing for more direct calculations of OV and EPE_interlayer. The optimized imaging conditions also enhance edge definition, improving pattern accuracy and process control. Our results show that SE and BSE imaging offer a more precise method for evaluating EPE and contribute to a better understanding of the factors influencing process window control.