Alignment Mark of Meta-Grating for Sub-10 Nanometer Overlay Inspection

Overlay error of multi-layer lithographic process is a critical parameter to determine final pattern quality and critical dimension and yield of integrated circuits. Therefore, a fast and accurate overlay metrology technique is essential to support the process and yield control. This paper proposes a moiré-based overlay metrology scheme by using one type of composite meta-grating mark. By capturing the moiré fringe generated by composite meta-grating with phase analysis, overlay measurement at sub-10 nanometer level is achieved. Simulations and experiments demonstrate that our scheme can achieve accurate overlay without the need of movement for repeated focusing, offering valuable insights for further exploration of overlay metrology and the related high-accuracy measurement technologies.