Through-pellicle imaging of extreme ultraviolet mask with extreme ultraviolet ptychography microscope

Abstract

Background: An extreme ultraviolet (EUV) pellicle is necessary to increase the process yield even though the declining throughput is a big concern. However, an EUV metrology/inspection tool for this pellicle has not been commercialized yet.

Aim: The goal of this study is to verify the pellicle/mask inspection feasibility of EUV scanning lensless imaging (ESLI) and verify the impact of contaminants on pellicles depending on their size.

Approach: Through-pellicle imaging was implemented by using ESLI, which uses a high-order harmonic generation EUV source and ptychography. Optical characteristics of various sizes of Fe-contaminated EUV pellicles were evaluated to verify their impact on wafer images.

Results: Large size (similar to 10 mu m) contaminants on the pellicle were found to contribute to the final wafer pattern loss. However, small size (2 to 3 mu m) contaminants on the pellicle do not have substantial impact on the wafer image.

Conclusions: The defect detection capability of ESLI for pellicle and mask was confirmed. Therefore, ESLI is useful in applications like pellicle qualification and EUV mask inspection metrology. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.