Simulation Analysis of Defect Repair Methods for EUVL Mo/Si Multilayer Mask Blanks

摘要

The availability of defect-free masks is a critical concern in EUV lithography. An intensive investigation of defectrepair methods for EUVL mask blanks is required because the mitigation of defects has turned out to be much moredifficult than anticipated. We investigated the effect of four methods through accurate simulations employing the FDTDmethod: 1) scooping a multilayer for amplitude defects, 2) EB exposure for phase defects, 3) covering a defect with anabsorber pattern, and 4) making intrusions in the absorber pattern near a defect. These methods create structural changesin the masks themselves. We calculated the aerial images of masks with such changes and compared them with that of aperfect mask. It was found that all the methods suppress the degradation in light intensity caused by defects. At the sametime, each repair method has some limitations and factors that require special attention. Thus, it is important to choosethe most suitable repair method for a given defect.