Development of standard samples with programmed defects for evaluation of pattern inspection tools for 7-nm and smaller nodes

Background: Continued shrinkage of pattern size has caused difficulties in detecting small defects. Multibeam scanning electron microscopy (SEM) is a potential method for pattern inspection below 7-nm node. Performance of the tool depends on charge control, resolution, and defect detection capability. Aim: The goal of this study is to develop a method for evaluating the performance of multibeam SEM for 7-nm nodes. Approach: By developing various standard samples with programmed defects (PDs) on 12 in. Si wafer, we evaluate the performance of multibeam SEM. Results: The first wafer had line and space (LS) patterns and PDs with varying contrast. A second wafer had various shaped small PDs, ∼5 nm in size in 16- to 12-nm half-pitch LS patterns. A third wafer with extremely small PDs of around 1 nm was fabricated in LS patterns with ultralow line-edge roughness (LER) of less than 1 nm. The first wafer was effective for charge control, whereas second and third wafer confirms resolution and defect detection capability. Conclusions: A set of minimum three standard wafer samples is effective to confirm the performance of multibeam SEM for below 7-nm nodes. Besides, we proposed a method to verify the LER values measured by a critical-dimension SEM.