As semiconductor integration goes down to nano-meter scale, finer patterning technology is inevitable. Therefore it is more and more important not only new lithographic development but also mask quality enhancement. Particularly, due to the delay of NGL technology, optical lithography is growing candidate for 65nm and beyond node device. In that case, mask CD uniformity and defect control issues are more important than ever. In mask inspection technology, there were a lot of new progresses to enhance the defect inspection sensitivity and stability via short-wavelength and advanced defect inspection algorithms. In this paper, we will present a concept and on going status of newly developed short-wavelength DUV inspection tool that is co-worked by Selete, Toshiba, and NEC. Moreover, we will discuss defect specifications that is required 65nm node and beyond technology node by simulations. This will include relations between defect inspectability and printability in the case of ArF, ArF immersion, and F2 lithography in various layouts and patterns. Through this study, we can conclude stable short-wavelength inspection tool and proper inspection algorithms are essential for future generation mask to cope with low k1 lithography.