Analysis of a low-aspect phase defect for actinic EUVL mask blank inspection

摘要

A high-volume manufacturing (HVM) actinic blank inspection (ABI) prototype could detect a printable phase defect for 16 nm node at almost 100 % of the capture rate. However, although a printable phase defect where the aspect ratio was lower than 0.01 was hardly existed, it was not detected by the HVM ABI prototype. For the purpose that could detect the low-aspect phase defects, scattered light angle from the defect was analyzed. As the result of analysis, an enlargement of the illumination NA was found to enhance the signal intensity of a low-aspect phase defect without any significant influence to the noise signal. The illumination optics of the HVM ABI prototype was improved and the illumination NA was enlarged from 0.07 to nearly 0.1. It was demonstrated that the low-aspect phase defect became to be detectable by the HVM ABI prototype, and no negative influence to other defects was found.