Innovative Cr shrinking to improve tritone mask process and inspectability

Abstract

For mature technology node IC manufacturing, a simple Tritone mask is widely adopted with chrome (Cr) layer remained in Scribe line and border region. The fabrication of a Tritone mask uses a dual step process with an e-beam writer for the 1st writing and a laser beam writer for the 2nd one, which induces process shift and possible Cr residual defects of the 2nd exposure writing. In this paper, NewRay Mask Technology Corporation (NRMTC) proposes a new process with adequate Cr shrinking, which can decrease residual Cr on Mosi/Qz edge when the mask is inspected and qualified on the KLA TeraScan™ 597XRS mask inspection system with Tritone Die-to-Database inspection mode. Furthermore, we have illustrated two main factors that contributed to Cr shrinking and figured out the optimal shrinking distance based on Cr line residue analysis and registration results. Production mask verification also conducted with optimal Cr shrink distance, demonstrates that optimal Cr shrinking distance can effectively improve the defect inspection process and have extra benefits on Tritone mask inspectability.