Study of EUV mask inspection technique using DUV light source for hp22nm and beyond

Abstract

EUV lithography is expected to be not only for hp 2Xnm node device production method but also for hp 1X nm node. We have already developed the mask inspection system using 199nm wavelength with simultaneous transmitted and reflected illumination optics, which utilize p-polarized and s-polarized illumination for high defect detection sensitivity, and we developed a new image contrast enhancement method which changes the digitizing rate of imaging sensor depending on the signal level. Also, we evaluate the mask structure which improve the image contrast and defect detection sensitivity. EUVL-mask has different configuration from transmitted type optical-mask. A captured image simulator has been developed to study the polarized illumination performance theoretically of our inspection system. Preferable mask structure for defect detection and possibility of miss defect detection are considered.