Abstract
The influence of the size or volume of the phase defect embedded in the extreme ultraviolet mask on wafer printability by scanning probe microscope (SPM) is well studied. However, only a few experimental results on the measurement accuracy of the phase defect size have been reported. Therefore, in this study, the measurement repeatability of the phase defect volume using SPM and the influence of the defect volume distribution on defect detection signal intensity (DSI) using an at-wavelength dark-field defect inspection tool were examined. A programmed phase defect mask was prepared, and a defect size measurement repeatability test was conducted using an SPM. As a result, the variation of the measured volume due to the measurement repeatability was much smaller than that of the defect-to-defect variation. This result indicates that measuring the volume of each phase defect is necessary in order to evaluate the defect detection yield using a phase defect inspection tool and wafer printability. In addition, the images of phase defects were captured using an at-wavelength dark-field inspection tool from which the defect DSIs were calculated. The DSI showed a direct correlation with the defect volume.
Highlights
Extreme ultraviolet lithography (EUVL) is considered to be the most promising next-generation lithography after the point where 193-nm immersion lithography will not be able to deliver smaller features
Regarding the types of defects, the nature of the pattern defects in the EUV mask is mostly the same as in the case of optical masks except for those defects that are classified as reflective multilayer defects, such as bump or pit phase defects that propagate through the multilayer during its deposition on the substrate surface, which are hard to repair.[17]
The phase defects were acquired in images using an actinic blank inspection (ABI) high-volume manufacturing (HVM) model (Lasertec Corporation, Yokohama, Japan)
Summary
Extreme ultraviolet lithography (EUVL) is considered to be the most promising next-generation lithography after the point where 193-nm immersion lithography will not be able to deliver smaller features. The reason is that for the EUVL generation, the device pattern feature size happens to be exceedingly small and calls for a higher repairing accuracy than would be required in optical lithography.[14,15,16] Regarding the types of defects, the nature of the pattern defects in the EUV mask is mostly the same as in the case of optical masks except for those defects that are classified as reflective multilayer defects, such as bump or pit phase defects that propagate through the multilayer during its deposition on the substrate surface, which are hard to repair.[17] to reduce the effect of a phase defect on the wafer printing image, two elimination methods are suggested. In order to make these methods succeed, it is necessary to measure the size or volume of the phase defects
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