Investigation of Defect Repair Methods for EUVL Mask Blanks through Aerial-Image Simulations

摘要

EUV lithography has become the leading candidate for pattern replication at the 32-nm technology node, but several important issues remain unresolved. In particular, the availability of defect-free masks is a critical concern. An intensive investigation of defect repair methods for EUVL mask blanks is required because the mitigation of defects has turned out to be much more difficult than anticipated. So, we investigated the effectiveness of several defect repair methods through accurate simulations employing the FDTD method. We calculated aerial images from masks with structural changes due to repair and compared them with those of a perfect mask. All the methods were found to suppress the degradation in light intensity caused by defects. At the same time, each repair method has some limitations and factors that require special attention. Thus, it is important to choose the most suitable repair method for a given defect.