Performance in practical use of actinic EUVL mask blank inspection

A high-volume manufacturing (HVM) actinic blank inspection (ABI) prototype has been developed, of which the inspection capability for a native defect was evaluated. An analysis of defect signal intensity (DSI) analysis showed that the DSI varied as a result of mask surface roughness. Operating the ABI under a review mode reduced that variation by 71 %, and therefore this operation was made available for precise DSI evaluation. The result also indicated that the defect capture rate was influenced by the DSI variation caused by mask surface roughness. A mask blank was inspected three times by the HVM ABI prototype, and impact of the detected native defects on wafer CD was evaluated. There was observed a pronounced relationship between the DSI and wafer CD; and this means that the ABI tool could detect wafer printable defects. Using the total DSI variation, the capture rate of the smallest defect critical for 16 nm node was estimated to be 93.2 %. This means that most of the critical defects for 16 nm node can be detected with the HVM ABI prototype.