Phase defect printability and mask inspection capability of 65-nm technology node Alt-PSM for ArF lithography (Photomask Japan Best Paper)

Abstract

The increase of MEEF(Mask Error Enhancement Factor) as well as the life prolonging of the ArF lithography with low k1 makes the demand for the mask quality more and more severe . Alt-PSM (Alternating Phase-Shifting Mask) is one of the most effective approaches to the resolution improvements of the ArF lithography. In addition, the improvement of MEEF can be expected in Alt-PSM . In this study, firstly Alt-PSM was manufactured containing programmed phase defects. The programmed phase defects are variable type and multiple phase angles. The phase differences of these defects are 180,120 and 60degree. Two types of chrome line width were placed (280nm and 400nm) with four different pitches (1:1.1:1.5,1:2,1:5). Two programmed phase defects type (divot and bump) placed on isolated and on edge. The printability of the phase defect was evaluated by using Aerial Image Measurement System (AIMS-fab193 of Carl Zeiss Co.) In this study, the printable defect was defined to be a defect, which CD error size is within +/-5% and DOF was +/-100nm on wafer. And, the defect detection capability was confirmed by using TeraScan( KLA-Tencor Co.) Finally, the real existence situation of the natural phase defect in imitated 65nm node production mask was estimated by using TeraScan with optimized inspection condition. In addition, the detected phase defect verified the printability. As a result of this verification, it turned out that a practical inspection was possible of Alt-PSM for 65nm technology node.