Lithographic qualification of new opaque MoSi binary mask blank for the 32-nm node and beyond

摘要

We discuss the lithographic qualification of a new type of binary mask blank consisting of an opaque layer of MoSi on a glass substrate, referred to simply as OMOG. First, OMOG lithographic performance will be compared to a previous chrome/MoSi/glass binary intensity mask (BIM) blank. Standard 70-nm chrome on class (COG) was not considered, as it failed to meet mask-making requirements. Theory and a series of simulation and experimental studies show OMOG to outperform BIM, particularly due to electromagnetic effects and optical proximity correction (OPC) predictability concerns, as OMOG behaves very similarly to the ideal thin mask approximation (TMA). A new TMA-predictability metric is defined as a means to compare mask blanks. We weigh the relative advantages and disadvantages of OMOG compared to 6% attenuated phase shifting. Although both mask blanks are likely sufficient for the 32-nm and 22-nm nodes, some differences exist and are described. Overall, however, of the blanks considered, it is concluded that OMOG provides the most robust and extendable imaging solution available for 32-nm and beyond.