Development of next generation mask inspection method by using the feature of mask image captured with 199 nm inspection optics

摘要

We have developed a mask inspection system using 199nm inspection light wavelength. This system performs transmission and reflection inspection processes concurrently within two hours per plate. By the evaluation result of mask images and inspection sensitivity, it is confirmed that the 199nm inspection system has the advantage over the system using 257nm and has the possibility corresponding to next generation mask inspection. Furthermore, advanced die-to-database (D-DB) inspection, which can generate high-fidelity of a reference image based on the CAD data for alternating phase shift mask (PSM) or tri-tone, is required for next generation inspection system, too. Therefore, a reference image generation method using two-layer CAD data has been developed. In this paper, the effectiveness of this method is described.