The Effect between Mask Blank Flatness and Wafer Print Process Window in ArF 6 Att. PSM Mask

摘要

Photomask blank flatness is more important for wafer lithography so far. In view of economic and capital concern, venders of mask blank always provide several level flatness of blank what mask house request. And the wafer fabricators would request the flatter photomask to fit the next generation requirement. The topography effect of photomask should be a contribution of lithography process window. The effect includes quartz substrate flatness and distortion and the film of Cr and MoSi deposit. Besides, the Mask blanks have several shapes that are flat, concave and convex. Reducing the effect from mask is the main consideration of depth of focus improvement. In this study, we made two masks of different type, 0.5T and 2.5T. Flatness measurement is directly provided by interferometer. To verify the effect between mask blank flatness and wafer printing window. Furthermore, we also check patterned mask effect of flatness. The pattern we use is poly layer of logical 90 nm generation that is more critical among all of lithography process and was exposed by 193nm ArF environment. Primary purpose of the ADI (after develop inspection) performance concern is process window of wafer print. Then, we offer the effected level between mask blank flatness and lithography process window.